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firefox/memory/build/mozjemalloc.cpp
Daniel Baumann 5e9a113729
Adding upstream version 140.0. 
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
2025-06-25 09:37:52 +02:00

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
// Portions of this file were originally under the following license:
//
// Copyright (C) 2006-2008 Jason Evans <jasone@FreeBSD.org>.
// All rights reserved.
// Copyright (C) 2007-2017 Mozilla Foundation.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
// notice(s), this list of conditions and the following disclaimer as
// the first lines of this file unmodified other than the possible
// addition of one or more copyright notices.
// 2. Redistributions in binary form must reproduce the above copyright
// notice(s), this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// *****************************************************************************
//
// This allocator implementation is designed to provide scalable performance
// for multi-threaded programs on multi-processor systems. The following
// features are included for this purpose:
//
// + Multiple arenas are used if there are multiple CPUs, which reduces lock
// contention and cache sloshing.
//
// + Cache line sharing between arenas is avoided for internal data
// structures.
//
// + Memory is managed in chunks and runs (chunks can be split into runs),
// rather than as individual pages. This provides a constant-time
// mechanism for associating allocations with particular arenas.
//
// Allocation requests are rounded up to the nearest size class, and no record
// of the original request size is maintained. Allocations are broken into
// categories according to size class. Assuming runtime defaults, the size
// classes in each category are as follows (for x86, x86_64 and Apple Silicon):
//
// |=========================================================|
// | Category | Subcategory | x86 | x86_64 | Mac ARM |
// |---------------------------+---------+---------+---------|
// | Word size | 32 bit | 64 bit | 64 bit |
// | Page size | 4 Kb | 4 Kb | 16 Kb |
// |=========================================================|
// | Small | Tiny | 4/-w | -w | - |
// | | | 8 | 8/-w | 8 |
// | |----------------+---------|---------|---------|
// | | Quantum-spaced | 16 | 16 | 16 |
// | | | 32 | 32 | 32 |
// | | | 48 | 48 | 48 |
// | | | ... | ... | ... |
// | | | 480 | 480 | 480 |
// | | | 496 | 496 | 496 |
// | |----------------+---------|---------|---------|
// | | Quantum-wide- | 512 | 512 | 512 |
// | | spaced | 768 | 768 | 768 |
// | | | ... | ... | ... |
// | | | 3584 | 3584 | 3584 |
// | | | 3840 | 3840 | 3840 |
// | |----------------+---------|---------|---------|
// | | Sub-page | - | - | 4096 |
// | | | - | - | 8 kB |
// |=========================================================|
// | Large | 4 kB | 4 kB | - |
// | | 8 kB | 8 kB | - |
// | | 12 kB | 12 kB | - |
// | | 16 kB | 16 kB | 16 kB |
// | | ... | ... | - |
// | | 32 kB | 32 kB | 32 kB |
// | | ... | ... | ... |
// | | 1008 kB | 1008 kB | 1008 kB |
// | | 1012 kB | 1012 kB | - |
// | | 1016 kB | 1016 kB | - |
// | | 1020 kB | 1020 kB | - |
// |=========================================================|
// | Huge | 1 MB | 1 MB | 1 MB |
// | | 2 MB | 2 MB | 2 MB |
// | | 3 MB | 3 MB | 3 MB |
// | | ... | ... | ... |
// |=========================================================|
//
// Legend:
// n: Size class exists for this platform.
// n/-w: This size class doesn't exist on Windows (see kMinTinyClass).
// -: This size class doesn't exist for this platform.
// ...: Size classes follow a pattern here.
//
// NOTE: Due to Mozilla bug 691003, we cannot reserve less than one word for an
// allocation on Linux or Mac. So on 32-bit *nix, the smallest bucket size is
// 4 bytes, and on 64-bit, the smallest bucket size is 8 bytes.
//
// A different mechanism is used for each category:
//
// Small : Each size class is segregated into its own set of runs. Each run
// maintains a bitmap of which regions are free/allocated.
//
// Large : Each allocation is backed by a dedicated run. Metadata are stored
// in the associated arena chunk header maps.
//
// Huge : Each allocation is backed by a dedicated contiguous set of chunks.
// Metadata are stored in a separate red-black tree.
//
// *****************************************************************************
#include "mozmemory_wrap.h"
#include "mozjemalloc.h"
#include "mozjemalloc_types.h"
#include <cstring>
#include <cerrno>
#include <chrono>
#include <optional>
#include <type_traits>
#ifdef XP_WIN
# include <io.h>
# include <windows.h>
#else
# include <sys/mman.h>
# include <unistd.h>
#endif
#ifdef XP_DARWIN
# include <libkern/OSAtomic.h>
# include <mach/mach_init.h>
# include <mach/vm_map.h>
#endif
#include "mozilla/Atomics.h"
#include "mozilla/Alignment.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/Assertions.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/DoublyLinkedList.h"
#include "mozilla/HelperMacros.h"
#include "mozilla/Likely.h"
#include "mozilla/Literals.h"
#include "mozilla/MathAlgorithms.h"
#include "mozilla/RandomNum.h"
// Note: MozTaggedAnonymousMmap() could call an LD_PRELOADed mmap
// instead of the one defined here; use only MozTagAnonymousMemory().
#include "mozilla/TaggedAnonymousMemory.h"
#include "mozilla/ThreadLocal.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"
#include "mozilla/XorShift128PlusRNG.h"
#include "mozilla/fallible.h"
#include "rb.h"
#include "Mutex.h"
#include "PHC.h"
#include "Utils.h"
#if defined(XP_WIN)
# include "mozmemory_utils.h"
#endif
// For GetGeckoProcessType(), when it's used.
#if defined(XP_WIN) && !defined(JS_STANDALONE)
# include "mozilla/ProcessType.h"
#endif
using namespace mozilla;
// On Linux, we use madvise(MADV_DONTNEED) to release memory back to the
// operating system. If we release 1MB of live pages with MADV_DONTNEED, our
// RSS will decrease by 1MB (almost) immediately.
//
// On Mac, we use madvise(MADV_FREE). Unlike MADV_DONTNEED on Linux, MADV_FREE
// on Mac doesn't cause the OS to release the specified pages immediately; the
// OS keeps them in our process until the machine comes under memory pressure.
//
// It's therefore difficult to measure the process's RSS on Mac, since, in the
// absence of memory pressure, the contribution from the heap to RSS will not
// decrease due to our madvise calls.
//
// We therefore define MALLOC_DOUBLE_PURGE on Mac. This causes jemalloc to
// track which pages have been MADV_FREE'd. You can then call
// jemalloc_purge_freed_pages(), which will force the OS to release those
// MADV_FREE'd pages, making the process's RSS reflect its true memory usage.
#ifdef XP_DARWIN
# define MALLOC_DOUBLE_PURGE
#endif
#ifdef XP_WIN
# define MALLOC_DECOMMIT
#endif
// Define MALLOC_RUNTIME_CONFIG depending on MOZ_DEBUG. Overriding this as
// a build option allows us to build mozjemalloc/firefox without runtime asserts
// but with runtime configuration. Making some testing easier.
#ifdef MOZ_DEBUG
# define MALLOC_RUNTIME_CONFIG
#endif
// Uncomment this to enable extra-vigilant assertions. These assertions may run
// more expensive checks that are sometimes too slow for regular debug mode.
// #define MALLOC_DEBUG_VIGILANT
// When MALLOC_STATIC_PAGESIZE is defined, the page size is fixed at
// compile-time for better performance, as opposed to determined at
// runtime. Some platforms can have different page sizes at runtime
// depending on kernel configuration, so they are opted out by default.
// Debug builds are opted out too, for test coverage.
#ifndef MALLOC_RUNTIME_CONFIG
# if !defined(__ia64__) && !defined(__sparc__) && !defined(__mips__) && \
!defined(__aarch64__) && !defined(__powerpc__) && !defined(XP_MACOSX) && \
!defined(__loongarch__)
# define MALLOC_STATIC_PAGESIZE 1
# endif
#endif
#ifdef XP_WIN
# define STDERR_FILENO 2
// Implement getenv without using malloc.
static char mozillaMallocOptionsBuf[64];
# define getenv xgetenv
static char* getenv(const char* name) {
if (GetEnvironmentVariableA(name, mozillaMallocOptionsBuf,
sizeof(mozillaMallocOptionsBuf)) > 0) {
return mozillaMallocOptionsBuf;
}
return nullptr;
}
#endif
#ifndef XP_WIN
// Newer Linux systems support MADV_FREE, but we're not supporting
// that properly. bug #1406304.
# if defined(XP_LINUX) && defined(MADV_FREE)
# undef MADV_FREE
# endif
# ifndef MADV_FREE
# define MADV_FREE MADV_DONTNEED
# endif
#endif
// Some tools, such as /dev/dsp wrappers, LD_PRELOAD libraries that
// happen to override mmap() and call dlsym() from their overridden
// mmap(). The problem is that dlsym() calls malloc(), and this ends
// up in a dead lock in jemalloc.
// On these systems, we prefer to directly use the system call.
// We do that for Linux systems and kfreebsd with GNU userland.
// Note sanity checks are not done (alignment of offset, ...) because
// the uses of mmap are pretty limited, in jemalloc.
//
// On Alpha, glibc has a bug that prevents syscall() to work for system
// calls with 6 arguments.
#if (defined(XP_LINUX) && !defined(__alpha__)) || \
(defined(__FreeBSD_kernel__) && defined(__GLIBC__))
# include <sys/syscall.h>
# if defined(SYS_mmap) || defined(SYS_mmap2)
static inline void* _mmap(void* addr, size_t length, int prot, int flags,
int fd, off_t offset) {
// S390 only passes one argument to the mmap system call, which is a
// pointer to a structure containing the arguments.
# ifdef __s390__
struct {
void* addr;
size_t length;
long prot;
long flags;
long fd;
off_t offset;
} args = {addr, length, prot, flags, fd, offset};
return (void*)syscall(SYS_mmap, &args);
# else
# if defined(ANDROID) && defined(__aarch64__) && defined(SYS_mmap2)
// Android NDK defines SYS_mmap2 for AArch64 despite it not supporting mmap2.
# undef SYS_mmap2
# endif
# ifdef SYS_mmap2
return (void*)syscall(SYS_mmap2, addr, length, prot, flags, fd, offset >> 12);
# else
return (void*)syscall(SYS_mmap, addr, length, prot, flags, fd, offset);
# endif
# endif
}
# define mmap _mmap
# define munmap(a, l) syscall(SYS_munmap, a, l)
# endif
#endif
// ***************************************************************************
// Structures for chunk headers for chunks used for non-huge allocations.
struct arena_t;
// Each element of the chunk map corresponds to one page within the chunk.
struct arena_chunk_map_t {
// Linkage for run trees. Used for arena_t's tree or available runs.
RedBlackTreeNode<arena_chunk_map_t> link;
// Run address (or size) and various flags are stored together. The bit
// layout looks like (assuming 32-bit system):
//
// ???????? ???????? ????---b fmckdzla
//
// ? : Unallocated: Run address for first/last pages, unset for internal
// pages.
// Small: Run address.
// Large: Run size for first page, unset for trailing pages.
// - : Unused.
// b : Busy?
// f : Fresh memory?
// m : MADV_FREE/MADV_DONTNEED'ed?
// c : decommitted?
// k : key?
// d : dirty?
// z : zeroed?
// l : large?
// a : allocated?
//
// Following are example bit patterns for consecutive pages from the three
// types of runs.
//
// r : run address
// s : run size
// x : don't care
// - : 0
// [cdzla] : bit set
//
// Unallocated:
// ssssssss ssssssss ssss---- --c-----
// xxxxxxxx xxxxxxxx xxxx---- ----d---
// ssssssss ssssssss ssss---- -----z--
//
// Note that the size fields are set for the first and last unallocated
// page only. The pages in-between have invalid/"don't care" size fields,
// they're not cleared during things such as coalescing free runs.
//
// Pages before the first or after the last page in a free run must be
// allocated or busy. Run coalescing depends on the sizes being set in
// the first and last page. Purging pages and releasing chunks require
// that unallocated pages are always coalesced and the first page has a
// correct size.
//
// Small:
// rrrrrrrr rrrrrrrr rrrr---- -------a
// rrrrrrrr rrrrrrrr rrrr---- -------a
// rrrrrrrr rrrrrrrr rrrr---- -------a
//
// Large:
// ssssssss ssssssss ssss---- ------la
// -------- -------- -------- ------la
// -------- -------- -------- ------la
//
// Note that only the first page has the size set.
//
size_t bits;
// A page can be in one of several states.
//
// CHUNK_MAP_ALLOCATED marks allocated pages, the only other bit that can be
// combined is CHUNK_MAP_LARGE.
//
// CHUNK_MAP_LARGE may be combined with CHUNK_MAP_ALLOCATED to show that the
// allocation is a "large" allocation (see SizeClass), rather than a run of
// small allocations. The interpretation of the gPageSizeMask bits depends onj
// this bit, see the description above.
//
// CHUNK_MAP_DIRTY is used to mark pages that were allocated and are now freed.
// They may contain their previous contents (or poison). CHUNK_MAP_DIRTY, when
// set, must be the only set bit.
//
// CHUNK_MAP_MADVISED marks pages which are madvised (with either MADV_DONTNEED
// or MADV_FREE). This is only valid if MALLOC_DECOMMIT is not defined. When
// set, it must be the only bit set.
//
// CHUNK_MAP_DECOMMITTED is used if CHUNK_MAP_DECOMMITTED is defined. Unused
// dirty pages may be decommitted and marked as CHUNK_MAP_DECOMMITTED. They
// must be re-committed with pages_commit() before they can be touched.
//
// CHUNK_MAP_FRESH is set on pages that have never been used before (the chunk
// is newly allocated or they were decommitted and have now been recommitted.
// CHUNK_MAP_FRESH is also used for "double purged" pages meaning that they were
// madvised and later were unmapped and remapped to force them out of the
// program's resident set. This is enabled when MALLOC_DOUBLE_PURGE is defined
// (eg on MacOS).
//
// CHUNK_MAP_BUSY is set by a thread when the thread wants to manipulate the
// pages without holding a lock. Other threads must not touch these pages
// regardless of whether they hold a lock.
//
// CHUNK_MAP_ZEROED is set on pages that are known to contain zeros.
//
// CHUNK_MAP_DIRTY, _DECOMMITED _MADVISED and _FRESH are always mutually
// exclusive.
//
// CHUNK_MAP_KEY is never used on real pages, only on lookup keys.
//
#define CHUNK_MAP_BUSY ((size_t)0x100U)
#define CHUNK_MAP_FRESH ((size_t)0x80U)
#define CHUNK_MAP_MADVISED ((size_t)0x40U)
#define CHUNK_MAP_DECOMMITTED ((size_t)0x20U)
#define CHUNK_MAP_MADVISED_OR_DECOMMITTED \
(CHUNK_MAP_MADVISED | CHUNK_MAP_DECOMMITTED)
#define CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED \
(CHUNK_MAP_FRESH | CHUNK_MAP_MADVISED | CHUNK_MAP_DECOMMITTED)
#define CHUNK_MAP_FRESH_MADVISED_DECOMMITTED_OR_BUSY \
(CHUNK_MAP_FRESH | CHUNK_MAP_MADVISED | CHUNK_MAP_DECOMMITTED | \
CHUNK_MAP_BUSY)
#define CHUNK_MAP_KEY ((size_t)0x10U)
#define CHUNK_MAP_DIRTY ((size_t)0x08U)
#define CHUNK_MAP_ZEROED ((size_t)0x04U)
#define CHUNK_MAP_LARGE ((size_t)0x02U)
#define CHUNK_MAP_ALLOCATED ((size_t)0x01U)
};
// Arena chunk header.
struct arena_chunk_t {
// Arena that owns the chunk.
arena_t* arena;
// Linkage for the arena's tree of dirty chunks.
RedBlackTreeNode<arena_chunk_t> link_dirty;
#ifdef MALLOC_DOUBLE_PURGE
// If we're double-purging, we maintain a linked list of chunks which
// have pages which have been madvise(MADV_FREE)'d but not explicitly
// purged.
//
// We're currently lazy and don't remove a chunk from this list when
// all its madvised pages are recommitted.
DoublyLinkedListElement<arena_chunk_t> chunks_madvised_elem;
#endif
// Number of dirty pages.
size_t ndirty;
bool mIsPurging;
bool mDying;
// Map of pages within chunk that keeps track of free/large/small.
arena_chunk_map_t map[]; // Dynamically sized.
bool IsEmpty();
};
// ***************************************************************************
// Constants defining allocator size classes and behavior.
// Our size classes are inclusive ranges of memory sizes. By describing the
// minimums and how memory is allocated in each range the maximums can be
// calculated.
// Smallest size class to support. On Windows the smallest allocation size
// must be 8 bytes on 32-bit, 16 bytes on 64-bit. On Linux and Mac, even
// malloc(1) must reserve a word's worth of memory (see Mozilla bug 691003).
#ifdef XP_WIN
static const size_t kMinTinyClass = sizeof(void*) * 2;
#else
static const size_t kMinTinyClass = sizeof(void*);
#endif
// Maximum tiny size class.
static const size_t kMaxTinyClass = 8;
// Smallest quantum-spaced size classes. It could actually also be labelled a
// tiny allocation, and is spaced as such from the largest tiny size class.
// Tiny classes being powers of 2, this is twice as large as the largest of
// them.
static const size_t kMinQuantumClass = kMaxTinyClass * 2;
static const size_t kMinQuantumWideClass = 512;
static const size_t kMinSubPageClass = 4_KiB;
// Amount (quantum) separating quantum-spaced size classes.
static const size_t kQuantum = 16;
static const size_t kQuantumMask = kQuantum - 1;
static const size_t kQuantumWide = 256;
static const size_t kQuantumWideMask = kQuantumWide - 1;
static const size_t kMaxQuantumClass = kMinQuantumWideClass - kQuantum;
static const size_t kMaxQuantumWideClass = kMinSubPageClass - kQuantumWide;
// We can optimise some divisions to shifts if these are powers of two.
static_assert(mozilla::IsPowerOfTwo(kQuantum),
"kQuantum is not a power of two");
static_assert(mozilla::IsPowerOfTwo(kQuantumWide),
"kQuantumWide is not a power of two");
static_assert(kMaxQuantumClass % kQuantum == 0,
"kMaxQuantumClass is not a multiple of kQuantum");
static_assert(kMaxQuantumWideClass % kQuantumWide == 0,
"kMaxQuantumWideClass is not a multiple of kQuantumWide");
static_assert(kQuantum < kQuantumWide,
"kQuantum must be smaller than kQuantumWide");
static_assert(mozilla::IsPowerOfTwo(kMinSubPageClass),
"kMinSubPageClass is not a power of two");
// Number of (2^n)-spaced tiny classes.
static const size_t kNumTinyClasses =
LOG2(kMaxTinyClass) - LOG2(kMinTinyClass) + 1;
// Number of quantum-spaced classes. We add kQuantum(Max) before subtracting to
// avoid underflow when a class is empty (Max<Min).
static const size_t kNumQuantumClasses =
(kMaxQuantumClass + kQuantum - kMinQuantumClass) / kQuantum;
static const size_t kNumQuantumWideClasses =
(kMaxQuantumWideClass + kQuantumWide - kMinQuantumWideClass) / kQuantumWide;
// Size and alignment of memory chunks that are allocated by the OS's virtual
// memory system.
static const size_t kChunkSize = 1_MiB;
static const size_t kChunkSizeMask = kChunkSize - 1;
#ifdef MALLOC_STATIC_PAGESIZE
// VM page size. It must divide the runtime CPU page size or the code
// will abort.
// Platform specific page size conditions copied from js/public/HeapAPI.h
# if defined(__powerpc64__)
static const size_t gPageSize = 64_KiB;
# elif defined(__loongarch64)
static const size_t gPageSize = 16_KiB;
# else
static const size_t gPageSize = 4_KiB;
# endif
static const size_t gRealPageSize = gPageSize;
#else
// When MALLOC_OPTIONS contains one or several `P`s, the page size used
// across the allocator is multiplied by 2 for each `P`, but we also keep
// the real page size for code paths that need it. gPageSize is thus a
// power of two greater or equal to gRealPageSize.
static size_t gRealPageSize;
static size_t gPageSize;
#endif
#ifdef MALLOC_STATIC_PAGESIZE
# define DECLARE_GLOBAL(type, name)
# define DEFINE_GLOBALS
# define END_GLOBALS
# define DEFINE_GLOBAL(type) static const type
# define GLOBAL_LOG2 LOG2
# define GLOBAL_ASSERT_HELPER1(x) static_assert(x, #x)
# define GLOBAL_ASSERT_HELPER2(x, y) static_assert(x, y)
# define GLOBAL_ASSERT(...) \
MACRO_CALL( \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(GLOBAL_ASSERT_HELPER, __VA_ARGS__), \
(__VA_ARGS__))
# define GLOBAL_CONSTEXPR constexpr
#else
# define DECLARE_GLOBAL(type, name) static type name;
# define DEFINE_GLOBALS static void DefineGlobals() {
# define END_GLOBALS }
# define DEFINE_GLOBAL(type)
# define GLOBAL_LOG2 FloorLog2
# define GLOBAL_ASSERT MOZ_RELEASE_ASSERT
# define GLOBAL_CONSTEXPR
#endif
DECLARE_GLOBAL(size_t, gMaxSubPageClass)
DECLARE_GLOBAL(uint8_t, gNumSubPageClasses)
DECLARE_GLOBAL(uint8_t, gPageSize2Pow)
DECLARE_GLOBAL(size_t, gPageSizeMask)
DECLARE_GLOBAL(size_t, gChunkNumPages)
DECLARE_GLOBAL(size_t, gChunkHeaderNumPages)
DECLARE_GLOBAL(size_t, gMaxLargeClass)
DEFINE_GLOBALS
// Largest sub-page size class, or zero if there are none
DEFINE_GLOBAL(size_t)
gMaxSubPageClass = gPageSize / 2 >= kMinSubPageClass ? gPageSize / 2 : 0;
// Max size class for bins.
#define gMaxBinClass \
(gMaxSubPageClass ? gMaxSubPageClass : kMaxQuantumWideClass)
// Number of sub-page bins.
DEFINE_GLOBAL(uint8_t)
gNumSubPageClasses = []() GLOBAL_CONSTEXPR -> uint8_t {
if GLOBAL_CONSTEXPR (gMaxSubPageClass != 0) {
return FloorLog2(gMaxSubPageClass) - LOG2(kMinSubPageClass) + 1;
}
return 0;
}();
DEFINE_GLOBAL(uint8_t) gPageSize2Pow = GLOBAL_LOG2(gPageSize);
DEFINE_GLOBAL(size_t) gPageSizeMask = gPageSize - 1;
// Number of pages in a chunk.
DEFINE_GLOBAL(size_t) gChunkNumPages = kChunkSize >> gPageSize2Pow;
// Number of pages necessary for a chunk header plus a guard page.
DEFINE_GLOBAL(size_t)
gChunkHeaderNumPages =
1 + (((sizeof(arena_chunk_t) + sizeof(arena_chunk_map_t) * gChunkNumPages +
gPageSizeMask) &
~gPageSizeMask) >>
gPageSize2Pow);
// One chunk, minus the header, minus a guard page
DEFINE_GLOBAL(size_t)
gMaxLargeClass =
kChunkSize - gPageSize - (gChunkHeaderNumPages << gPageSize2Pow);
// Various sanity checks that regard configuration.
GLOBAL_ASSERT(1ULL << gPageSize2Pow == gPageSize,
"Page size is not a power of two");
GLOBAL_ASSERT(kQuantum >= sizeof(void*));
GLOBAL_ASSERT(kQuantum <= kQuantumWide);
GLOBAL_ASSERT(!kNumQuantumWideClasses ||
kQuantumWide <= (kMinSubPageClass - kMaxQuantumClass));
GLOBAL_ASSERT(kQuantumWide <= kMaxQuantumClass);
GLOBAL_ASSERT(gMaxSubPageClass >= kMinSubPageClass || gMaxSubPageClass == 0);
GLOBAL_ASSERT(gMaxLargeClass >= gMaxSubPageClass);
GLOBAL_ASSERT(kChunkSize >= gPageSize);
GLOBAL_ASSERT(kQuantum * 4 <= kChunkSize);
END_GLOBALS
// Recycle at most 128 MiB of chunks. This means we retain at most
// 6.25% of the process address space on a 32-bit OS for later use.
static const size_t gRecycleLimit = 128_MiB;
// The current amount of recycled bytes, updated atomically.
static Atomic<size_t> gRecycledSize;
// Maximum number of dirty pages per arena.
#define DIRTY_MAX_DEFAULT (1U << 8)
static size_t opt_dirty_max = DIRTY_MAX_DEFAULT;
// Return the smallest chunk multiple that is >= s.
#define CHUNK_CEILING(s) (((s) + kChunkSizeMask) & ~kChunkSizeMask)
// Return the smallest cacheline multiple that is >= s.
#define CACHELINE_CEILING(s) \
(((s) + (kCacheLineSize - 1)) & ~(kCacheLineSize - 1))
// Return the smallest quantum multiple that is >= a.
#define QUANTUM_CEILING(a) (((a) + (kQuantumMask)) & ~(kQuantumMask))
#define QUANTUM_WIDE_CEILING(a) \
(((a) + (kQuantumWideMask)) & ~(kQuantumWideMask))
// Return the smallest sub page-size that is >= a.
#define SUBPAGE_CEILING(a) (RoundUpPow2(a))
// Return the smallest pagesize multiple that is >= s.
#define PAGE_CEILING(s) (((s) + gPageSizeMask) & ~gPageSizeMask)
// Number of all the small-allocated classes
#define NUM_SMALL_CLASSES \
(kNumTinyClasses + kNumQuantumClasses + kNumQuantumWideClasses + \
gNumSubPageClasses)
// ***************************************************************************
// MALLOC_DECOMMIT and MALLOC_DOUBLE_PURGE are mutually exclusive.
#if defined(MALLOC_DECOMMIT) && defined(MALLOC_DOUBLE_PURGE)
# error MALLOC_DECOMMIT and MALLOC_DOUBLE_PURGE are mutually exclusive.
#endif
static void* base_alloc(size_t aSize);
// Set to true once the allocator has been initialized.
#if defined(_MSC_VER) && !defined(__clang__)
// MSVC may create a static initializer for an Atomic<bool>, which may actually
// run after `malloc_init` has been called once, which triggers multiple
// initializations.
// We work around the problem by not using an Atomic<bool> at all. There is a
// theoretical problem with using `malloc_initialized` non-atomically, but
// practically, this is only true if `malloc_init` is never called before
// threads are created.
static bool malloc_initialized;
#else
// We can rely on Relaxed here because this variable is only ever set when
// holding gInitLock. A thread that still sees it false while another sets it
// true will enter the same lock, synchronize with the former and check the
// flag again under the lock.
static Atomic<bool, MemoryOrdering::Relaxed> malloc_initialized;
#endif
// This lock must be held while bootstrapping us.
static StaticMutex gInitLock MOZ_UNANNOTATED = {STATIC_MUTEX_INIT};
// ***************************************************************************
// Statistics data structures.
struct arena_stats_t {
// Number of bytes currently mapped.
size_t mapped;
// Current number of committed pages (non madvised/decommitted)
size_t committed;
// Per-size-category statistics.
size_t allocated_small;
size_t allocated_large;
// The number of "memory operations" aka mallocs/frees.
uint64_t operations;
};
// ***************************************************************************
// Extent data structures.
enum ChunkType {
UNKNOWN_CHUNK,
ZEROED_CHUNK, // chunk only contains zeroes.
ARENA_CHUNK, // used to back arena runs created by arena_t::AllocRun.
HUGE_CHUNK, // used to back huge allocations (e.g. arena_t::MallocHuge).
RECYCLED_CHUNK, // chunk has been stored for future use by chunk_recycle.
};
// Tree of extents.
struct extent_node_t {
union {
// Linkage for the size/address-ordered tree for chunk recycling.
RedBlackTreeNode<extent_node_t> mLinkBySize;
// Arena id for huge allocations. It's meant to match mArena->mId,
// which only holds true when the arena hasn't been disposed of.
arena_id_t mArenaId;
};
// Linkage for the address-ordered tree.
RedBlackTreeNode<extent_node_t> mLinkByAddr;
// Pointer to the extent that this tree node is responsible for.
void* mAddr;
// Total region size.
size_t mSize;
union {
// What type of chunk is there; used for chunk recycling.
ChunkType mChunkType;
// A pointer to the associated arena, for huge allocations.
arena_t* mArena;
};
};
struct ExtentTreeSzTrait {
static RedBlackTreeNode<extent_node_t>& GetTreeNode(extent_node_t* aThis) {
return aThis->mLinkBySize;
}
static inline Order Compare(extent_node_t* aNode, extent_node_t* aOther) {
Order ret = CompareInt(aNode->mSize, aOther->mSize);
return (ret != Order::eEqual) ? ret
: CompareAddr(aNode->mAddr, aOther->mAddr);
}
};
struct ExtentTreeTrait {
static RedBlackTreeNode<extent_node_t>& GetTreeNode(extent_node_t* aThis) {
return aThis->mLinkByAddr;
}
static inline Order Compare(extent_node_t* aNode, extent_node_t* aOther) {
return CompareAddr(aNode->mAddr, aOther->mAddr);
}
};
struct ExtentTreeBoundsTrait : public ExtentTreeTrait {
static inline Order Compare(extent_node_t* aKey, extent_node_t* aNode) {
uintptr_t key_addr = reinterpret_cast<uintptr_t>(aKey->mAddr);
uintptr_t node_addr = reinterpret_cast<uintptr_t>(aNode->mAddr);
size_t node_size = aNode->mSize;
// Is aKey within aNode?
if (node_addr <= key_addr && key_addr < node_addr + node_size) {
return Order::eEqual;
}
return CompareAddr(aKey->mAddr, aNode->mAddr);
}
};
// Describe size classes to which allocations are rounded up to.
// TODO: add large and huge types when the arena allocation code
// changes in a way that allows it to be beneficial.
class SizeClass {
public:
enum ClassType {
Tiny,
Quantum,
QuantumWide,
SubPage,
Large,
};
explicit inline SizeClass(size_t aSize) {
if (aSize <= kMaxTinyClass) {
mType = Tiny;
mSize = std::max(RoundUpPow2(aSize), kMinTinyClass);
} else if (aSize <= kMaxQuantumClass) {
mType = Quantum;
mSize = QUANTUM_CEILING(aSize);
} else if (aSize <= kMaxQuantumWideClass) {
mType = QuantumWide;
mSize = QUANTUM_WIDE_CEILING(aSize);
} else if (aSize <= gMaxSubPageClass) {
mType = SubPage;
mSize = SUBPAGE_CEILING(aSize);
} else if (aSize <= gMaxLargeClass) {
mType = Large;
mSize = PAGE_CEILING(aSize);
} else {
MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Invalid size");
}
}
SizeClass& operator=(const SizeClass& aOther) = default;
bool operator==(const SizeClass& aOther) { return aOther.mSize == mSize; }
size_t Size() { return mSize; }
ClassType Type() { return mType; }
SizeClass Next() { return SizeClass(mSize + 1); }
private:
ClassType mType;
size_t mSize;
};
// Fast division
//
// During deallocation we want to divide by the size class. This class
// provides a routine and sets up a constant as follows.
//
// To divide by a number D that is not a power of two we multiply by (2^17 /
// D) and then right shift by 17 positions.
//
// X / D
//
// becomes
//
// (X * m) >> p
//
// Where m is calculated during the FastDivisor constructor similarly to:
//
// m = 2^p / D
//
template <typename T>
class FastDivisor {
private:
// The shift amount (p) is chosen to minimise the size of m while
// working for divisors up to 65536 in steps of 16. I arrived at 17
// experimentally. I wanted a low number to minimise the range of m
// so it can fit in a uint16_t, 16 didn't work but 17 worked perfectly.
//
// We'd need to increase this if we allocated memory on smaller boundaries
// than 16.
static const unsigned p = 17;
// We can fit the inverted divisor in 16 bits, but we template it here for
// convenience.
T m;
public:
// Needed so mBins can be constructed.
FastDivisor() : m(0) {}
FastDivisor(unsigned div, unsigned max) {
MOZ_ASSERT(div <= max);
// divide_inv_shift is large enough.
MOZ_ASSERT((1U << p) >= div);
// The calculation here for m is formula 26 from Section
// 10-9 "Unsigned Division by Divisors >= 1" in
// Henry S. Warren, Jr.'s Hacker's Delight, 2nd Ed.
unsigned m_ = ((1U << p) + div - 1 - (((1U << p) - 1) % div)) / div;
// Make sure that max * m does not overflow.
MOZ_DIAGNOSTIC_ASSERT(max < UINT_MAX / m_);
MOZ_ASSERT(m_ <= std::numeric_limits<T>::max());
m = static_cast<T>(m_);
// Initialisation made m non-zero.
MOZ_ASSERT(m);
// Test that all the divisions in the range we expected would work.
#ifdef MOZ_DEBUG
for (unsigned num = 0; num < max; num += div) {
MOZ_ASSERT(num / div == divide(num));
}
#endif
}
// Note that this always occurs in uint32_t regardless of m's type. If m is
// a uint16_t it will be zero-extended before the multiplication. We also use
// uint32_t rather than something that could possibly be larger because it is
// most-likely the cheapest multiplication.
inline uint32_t divide(uint32_t num) const {
// Check that m was initialised.
MOZ_ASSERT(m);
return (num * m) >> p;
}
};
template <typename T>
unsigned inline operator/(unsigned num, FastDivisor<T> divisor) {
return divisor.divide(num);
}
// ***************************************************************************
// Radix tree data structures.
//
// The number of bits passed to the template is the number of significant bits
// in an address to do a radix lookup with.
//
// An address is looked up by splitting it in kBitsPerLevel bit chunks, except
// the most significant bits, where the bit chunk is kBitsAtLevel1 which can be
// different if Bits is not a multiple of kBitsPerLevel.
//
// With e.g. sizeof(void*)=4, Bits=16 and kBitsPerLevel=8, an address is split
// like the following:
// 0x12345678 -> mRoot[0x12][0x34]
template <size_t Bits>
class AddressRadixTree {
// Size of each radix tree node (as a power of 2).
// This impacts tree depth.
#ifdef HAVE_64BIT_BUILD
static const size_t kNodeSize = kCacheLineSize;
#else
static const size_t kNodeSize = 16_KiB;
#endif
static const size_t kBitsPerLevel = LOG2(kNodeSize) - LOG2(sizeof(void*));
static const size_t kBitsAtLevel1 =
(Bits % kBitsPerLevel) ? Bits % kBitsPerLevel : kBitsPerLevel;
static const size_t kHeight = (Bits + kBitsPerLevel - 1) / kBitsPerLevel;
static_assert(kBitsAtLevel1 + (kHeight - 1) * kBitsPerLevel == Bits,
"AddressRadixTree parameters don't work out");
Mutex mLock MOZ_UNANNOTATED;
// We guard only the single slot creations and assume read-only is safe
// at any time.
void** mRoot;
public:
bool Init() MOZ_REQUIRES(gInitLock) MOZ_EXCLUDES(mLock);
inline void* Get(void* aAddr) MOZ_EXCLUDES(mLock);
// Returns whether the value was properly set.
inline bool Set(void* aAddr, void* aValue) MOZ_EXCLUDES(mLock);
inline bool Unset(void* aAddr) MOZ_EXCLUDES(mLock) {
return Set(aAddr, nullptr);
}
private:
// GetSlotInternal is agnostic wrt mLock and used directly only in DEBUG
// code.
inline void** GetSlotInternal(void* aAddr, bool aCreate);
inline void** GetSlotIfExists(void* aAddr) MOZ_EXCLUDES(mLock) {
return GetSlotInternal(aAddr, false);
}
inline void** GetOrCreateSlot(void* aAddr) MOZ_REQUIRES(mLock) {
return GetSlotInternal(aAddr, true);
}
};
// ***************************************************************************
// Arena data structures.
struct arena_bin_t;
struct ArenaChunkMapLink {
static RedBlackTreeNode<arena_chunk_map_t>& GetTreeNode(
arena_chunk_map_t* aThis) {
return aThis->link;
}
};
struct ArenaAvailTreeTrait : public ArenaChunkMapLink {
static inline Order Compare(arena_chunk_map_t* aNode,
arena_chunk_map_t* aOther) {
size_t size1 = aNode->bits & ~gPageSizeMask;
size_t size2 = aOther->bits & ~gPageSizeMask;
Order ret = CompareInt(size1, size2);
return (ret != Order::eEqual)
? ret
: CompareAddr((aNode->bits & CHUNK_MAP_KEY) ? nullptr : aNode,
aOther);
}
};
struct ArenaDirtyChunkTrait {
static RedBlackTreeNode<arena_chunk_t>& GetTreeNode(arena_chunk_t* aThis) {
return aThis->link_dirty;
}
static inline Order Compare(arena_chunk_t* aNode, arena_chunk_t* aOther) {
MOZ_ASSERT(aNode);
MOZ_ASSERT(aOther);
return CompareAddr(aNode, aOther);
}
};
#ifdef MALLOC_DOUBLE_PURGE
namespace mozilla {
template <>
struct GetDoublyLinkedListElement<arena_chunk_t> {
static DoublyLinkedListElement<arena_chunk_t>& Get(arena_chunk_t* aThis) {
return aThis->chunks_madvised_elem;
}
};
} // namespace mozilla
#endif
enum class purge_action_t {
None,
PurgeNow,
Queue,
};
struct arena_run_t {
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
uint32_t mMagic;
# define ARENA_RUN_MAGIC 0x384adf93
// On 64-bit platforms, having the arena_bin_t pointer following
// the mMagic field means there's padding between both fields, making
// the run header larger than necessary.
// But when MOZ_DIAGNOSTIC_ASSERT_ENABLED is not set, starting the
// header with this field followed by the arena_bin_t pointer yields
// the same padding. We do want the mMagic field to appear first, so
// depending whether MOZ_DIAGNOSTIC_ASSERT_ENABLED is set or not, we
// move some field to avoid padding.
// Number of free regions in run.
unsigned mNumFree;
#endif
// Used by arena_bin_t::mNonFullRuns.
DoublyLinkedListElement<arena_run_t> mRunListElem;
// Bin this run is associated with.
arena_bin_t* mBin;
// Index of first element that might have a free region.
unsigned mRegionsMinElement;
#if !defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
// Number of free regions in run.
unsigned mNumFree;
#endif
// Bitmask of in-use regions (0: in use, 1: free).
unsigned mRegionsMask[]; // Dynamically sized.
};
namespace mozilla {
template <>
struct GetDoublyLinkedListElement<arena_run_t> {
static DoublyLinkedListElement<arena_run_t>& Get(arena_run_t* aThis) {
return aThis->mRunListElem;
}
};
} // namespace mozilla
struct arena_bin_t {
// We use a LIFO ("last-in-first-out") policy to refill non-full runs.
//
// This has the following reasons:
// 1. It is cheap, as all our non-full-runs' book-keeping is O(1), no
// tree-balancing or walking is needed.
// 2. It also helps to increase the probability for CPU cache hits for the
// book-keeping and the reused slots themselves, as the same memory was
// most recently touched during free, especially when used from the same
// core (or via the same shared cache, depending on the architecture).
DoublyLinkedList<arena_run_t> mNonFullRuns;
// Bin's size class.
size_t mSizeClass;
// Total number of regions in a run for this bin's size class.
uint32_t mRunNumRegions;
// Number of elements in a run's mRegionsMask for this bin's size class.
uint32_t mRunNumRegionsMask;
// Offset of first region in a run for this bin's size class.
uint32_t mRunFirstRegionOffset;
// Current number of runs in this bin, full or otherwise.
uint32_t mNumRuns;
// A constant for fast division by size class. This value is 16 bits wide so
// it is placed last.
FastDivisor<uint16_t> mSizeDivisor;
// Total number of pages in a run for this bin's size class.
uint8_t mRunSizePages;
// Amount of overhead runs are allowed to have.
static constexpr double kRunOverhead = 1.6_percent;
static constexpr double kRunRelaxedOverhead = 2.4_percent;
// Initialize a bin for the given size class.
// The generated run sizes, for a page size of 4 KiB, are:
// size|run size|run size|run size|run
// class|size class|size class|size class|size
// 4 4 KiB 8 4 KiB 16 4 KiB 32 4 KiB
// 48 4 KiB 64 4 KiB 80 4 KiB 96 4 KiB
// 112 4 KiB 128 8 KiB 144 4 KiB 160 8 KiB
// 176 4 KiB 192 4 KiB 208 8 KiB 224 4 KiB
// 240 8 KiB 256 16 KiB 272 8 KiB 288 4 KiB
// 304 12 KiB 320 12 KiB 336 4 KiB 352 8 KiB
// 368 4 KiB 384 8 KiB 400 20 KiB 416 16 KiB
// 432 12 KiB 448 4 KiB 464 16 KiB 480 8 KiB
// 496 20 KiB 512 32 KiB 768 16 KiB 1024 64 KiB
// 1280 24 KiB 1536 32 KiB 1792 16 KiB 2048 128 KiB
// 2304 16 KiB 2560 48 KiB 2816 36 KiB 3072 64 KiB
// 3328 36 KiB 3584 32 KiB 3840 64 KiB
inline void Init(SizeClass aSizeClass);
};
// We try to keep the above structure aligned with common cache lines sizes,
// often that's 64 bytes on x86 and ARM, we don't make assumptions for other
// architectures.
#if defined(__x86_64__) || defined(__aarch64__)
// On 64bit platforms this structure is often 48 bytes
// long, which means every other array element will be properly aligned.
static_assert(sizeof(arena_bin_t) == 48);
#elif defined(__x86__) || defined(__arm__)
static_assert(sizeof(arena_bin_t) == 32);
#endif
// We cannot instantiate
// Atomic<std::chrono::time_point<std::chrono::steady_clock>>
// so we explicitly force timestamps to be uint64_t in ns.
uint64_t GetTimestampNS() {
// On most if not all systems we care about the conversion to ns is a no-op,
// so we prefer to keep the precision here for performance, but let's be
// explicit about it.
return std::chrono::floor<std::chrono::nanoseconds>(
std::chrono::steady_clock::now())
.time_since_epoch()
.count();
}
enum PurgeCondition { PurgeIfThreshold, PurgeUnconditional };
struct arena_t {
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
uint32_t mMagic;
# define ARENA_MAGIC 0x947d3d24
#endif
// Linkage for the tree of arenas by id.
// This just provides the memory to be used by the collection tree
// and thus needs no arena_t::mLock.
RedBlackTreeNode<arena_t> mLink;
// Arena id, that we keep away from the beginning of the struct so that
// free list pointers in TypedBaseAlloc<arena_t> don't overflow in it,
// and it keeps the value it had after the destructor.
arena_id_t mId;
// Operations on this arena require that lock be locked. The MaybeMutex
// class will elude locking if the arena is accessed from a single thread
// only (currently only the main thread can be used like this).
// Can be acquired while holding gArenas.mLock, but must not be acquired or
// held while holding or acquiring gArenas.mPurgeListLock.
MaybeMutex mLock MOZ_UNANNOTATED;
// The lock is required to write to fields of mStats, but it is not needed to
// read them, so long as inconsistents reads are okay (fields might not make
// sense together).
arena_stats_t mStats MOZ_GUARDED_BY(mLock);
// We can read the allocated counts from mStats without a lock:
size_t AllocatedBytes() const MOZ_NO_THREAD_SAFETY_ANALYSIS {
return mStats.allocated_small + mStats.allocated_large;
}
// We can read the operations field from mStats without a lock:
uint64_t Operations() const MOZ_NO_THREAD_SAFETY_ANALYSIS {
return mStats.operations;
}
private:
// Tree of dirty-page-containing chunks this arena manages.
RedBlackTree<arena_chunk_t, ArenaDirtyChunkTrait> mChunksDirty
MOZ_GUARDED_BY(mLock);
#ifdef MALLOC_DOUBLE_PURGE
// Head of a linked list of MADV_FREE'd-page-containing chunks this
// arena manages.
DoublyLinkedList<arena_chunk_t> mChunksMAdvised MOZ_GUARDED_BY(mLock);
#endif
// In order to avoid rapid chunk allocation/deallocation when an arena
// oscillates right on the cusp of needing a new chunk, cache the most
// recently freed chunk. The spare is left in the arena's chunk trees
// until it is deleted.
//
// There is one spare chunk per arena, rather than one spare total, in
// order to avoid interactions between multiple threads that could make
// a single spare inadequate.
arena_chunk_t* mSpare MOZ_GUARDED_BY(mLock);
// A per-arena opt-in to randomize the offset of small allocations
// Needs no lock, read-only.
bool mRandomizeSmallAllocations;
// A pseudorandom number generator. Initially null, it gets initialized
// on first use to avoid recursive malloc initialization (e.g. on OSX
// arc4random allocates memory).
mozilla::non_crypto::XorShift128PlusRNG* mPRNG MOZ_GUARDED_BY(mLock);
bool mIsPRNGInitializing MOZ_GUARDED_BY(mLock);
public:
// Whether this is a private arena. Multiple public arenas are just a
// performance optimization and not a safety feature.
//
// Since, for example, we don't want thread-local arenas to grow too much, we
// use the default arena for bigger allocations. We use this member to allow
// realloc() to switch out of our arena if needed (which is not allowed for
// private arenas for security).
// Needs no lock, read-only.
bool mIsPrivate;
// Current count of pages within unused runs that are potentially
// dirty, and for which madvise(... MADV_FREE) has not been called. By
// tracking this, we can institute a limit on how much dirty unused
// memory is mapped for each arena.
size_t mNumDirty MOZ_GUARDED_BY(mLock);
// Precalculated value for faster checks.
size_t mMaxDirty MOZ_GUARDED_BY(mLock);
// The current number of pages that are available without a system call (but
// probably a page fault).
size_t mNumMAdvised MOZ_GUARDED_BY(mLock);
size_t mNumFresh MOZ_GUARDED_BY(mLock);
// Maximum value allowed for mNumDirty.
// Needs no lock, read-only.
size_t mMaxDirtyBase;
// Needs no lock, read-only.
int32_t mMaxDirtyIncreaseOverride;
int32_t mMaxDirtyDecreaseOverride;
// The link to gArenas.mOutstandingPurges.
// Note that this must only be accessed while holding gArenas.mPurgeListLock
// (but not arena_t.mLock !) through gArenas.mOutstandingPurges.
DoublyLinkedListElement<arena_t> mPurgeListElem;
// A "significant reuse" is when a dirty page is used for a new allocation,
// it has the CHUNK_MAP_DIRTY bit cleared and CHUNK_MAP_ALLOCATED set.
//
// Timestamp of the last time we saw a significant reuse (in ns).
// Note that this variable is written very often from many threads and read
// only sparsely on the main thread, but when we read it we need to see the
// chronologically latest write asap (so we cannot use Relaxed).
Atomic<uint64_t> mLastSignificantReuseNS;
public:
// A flag that indicates if arena will be Purge()'d.
//
// It is set either when a thread commits to adding it to mOutstandingPurges
// or when imitating a Purge. Cleared only by Purge when we know we are
// completely done. This is used to avoid accessing the list (and list lock)
// on every call to ShouldStartPurge() and to avoid deleting arenas that
// another thread is purging.
bool mIsPurgePending MOZ_GUARDED_BY(mLock);
// A mirror of ArenaCollection::mIsDeferredPurgeEnabled, here only to
// optimize memory reads in ShouldStartPurge().
bool mIsDeferredPurgeEnabled MOZ_GUARDED_BY(mLock);
// True if the arena is in the process of being destroyed, and needs to be
// released after a concurrent purge completes.
bool mMustDeleteAfterPurge MOZ_GUARDED_BY(mLock) = false;
private:
// Size/address-ordered tree of this arena's available runs. This tree
// is used for first-best-fit run allocation.
RedBlackTree<arena_chunk_map_t, ArenaAvailTreeTrait> mRunsAvail
MOZ_GUARDED_BY(mLock);
public:
// mBins is used to store rings of free regions of the following sizes,
// assuming a 16-byte quantum, 4kB pagesize, and default MALLOC_OPTIONS.
//
// | mBins[i] | size |
// +----------+------+
// | 0 | 2 |
// | 1 | 4 |
// | 2 | 8 |
// +----------+------+
// | 3 | 16 |
// | 4 | 32 |
// | 5 | 48 |
// | 6 | 64 |
// | : :
// | : :
// | 33 | 496 |
// | 34 | 512 |
// +----------+------+
// | 35 | 768 |
// | 36 | 1024 |
// | : :
// | : :
// | 46 | 3584 |
// | 47 | 3840 |
// +----------+------+
arena_bin_t mBins[] MOZ_GUARDED_BY(mLock); // Dynamically sized.
explicit arena_t(arena_params_t* aParams, bool aIsPrivate);
~arena_t();
void ResetSmallAllocRandomization();
void InitPRNG() MOZ_REQUIRES(mLock);
private:
void InitChunk(arena_chunk_t* aChunk, size_t aMinCommittedPages)
MOZ_REQUIRES(mLock);
// Remove the chunk from the arena. This removes it from all the page counts.
// It assumes its run has already been removed and lets the caller clear
// mSpare as necessary.
bool RemoveChunk(arena_chunk_t* aChunk) MOZ_REQUIRES(mLock);
// This may return a chunk that should be destroyed with chunk_dealloc outside
// of the arena lock. It is not the same chunk as was passed in (since that
// chunk now becomes mSpare).
[[nodiscard]] arena_chunk_t* DemoteChunkToSpare(arena_chunk_t* aChunk)
MOZ_REQUIRES(mLock);
// Try to merge the run with its neighbours. Returns the new index of the run
// (since it may have merged with an earlier one).
size_t TryCoalesce(arena_chunk_t* aChunk, size_t run_ind, size_t run_pages,
size_t size) MOZ_REQUIRES(mLock);
arena_run_t* AllocRun(size_t aSize, bool aLarge, bool aZero)
MOZ_REQUIRES(mLock);
arena_chunk_t* DallocRun(arena_run_t* aRun, bool aDirty) MOZ_REQUIRES(mLock);
[[nodiscard]] bool SplitRun(arena_run_t* aRun, size_t aSize, bool aLarge,
bool aZero) MOZ_REQUIRES(mLock);
void TrimRunHead(arena_chunk_t* aChunk, arena_run_t* aRun, size_t aOldSize,
size_t aNewSize) MOZ_REQUIRES(mLock);
void TrimRunTail(arena_chunk_t* aChunk, arena_run_t* aRun, size_t aOldSize,
size_t aNewSize, bool dirty) MOZ_REQUIRES(mLock);
arena_run_t* GetNewEmptyBinRun(arena_bin_t* aBin) MOZ_REQUIRES(mLock);
inline arena_run_t* GetNonFullBinRun(arena_bin_t* aBin) MOZ_REQUIRES(mLock);
inline uint8_t FindFreeBitInMask(uint32_t aMask, uint32_t& aRng)
MOZ_REQUIRES(mLock);
inline void* ArenaRunRegAlloc(arena_run_t* aRun, arena_bin_t* aBin)
MOZ_REQUIRES(mLock);
inline void* MallocSmall(size_t aSize, bool aZero) MOZ_EXCLUDES(mLock);
void* MallocLarge(size_t aSize, bool aZero) MOZ_EXCLUDES(mLock);
void* MallocHuge(size_t aSize, bool aZero) MOZ_EXCLUDES(mLock);
void* PallocLarge(size_t aAlignment, size_t aSize, size_t aAllocSize)
MOZ_EXCLUDES(mLock);
void* PallocHuge(size_t aSize, size_t aAlignment, bool aZero)
MOZ_EXCLUDES(mLock);
void RallocShrinkLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
size_t aOldSize) MOZ_EXCLUDES(mLock);
bool RallocGrowLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
size_t aOldSize) MOZ_EXCLUDES(mLock);
void* RallocSmallOrLarge(void* aPtr, size_t aSize, size_t aOldSize)
MOZ_EXCLUDES(mLock);
void* RallocHuge(void* aPtr, size_t aSize, size_t aOldSize)
MOZ_EXCLUDES(mLock);
public:
inline void* Malloc(size_t aSize, bool aZero) MOZ_EXCLUDES(mLock);
void* Palloc(size_t aAlignment, size_t aSize) MOZ_EXCLUDES(mLock);
// This may return a chunk that should be destroyed with chunk_dealloc outside
// of the arena lock. It is not the same chunk as was passed in (since that
// chunk now becomes mSpare).
[[nodiscard]] inline arena_chunk_t* DallocSmall(arena_chunk_t* aChunk,
void* aPtr,
arena_chunk_map_t* aMapElm)
MOZ_REQUIRES(mLock);
[[nodiscard]] arena_chunk_t* DallocLarge(arena_chunk_t* aChunk, void* aPtr)
MOZ_REQUIRES(mLock);
void* Ralloc(void* aPtr, size_t aSize, size_t aOldSize) MOZ_EXCLUDES(mLock);
void UpdateMaxDirty() MOZ_EXCLUDES(mLock);
#ifdef MALLOC_DECOMMIT
// During a commit operation (for aReqPages) we have the opportunity of
// commiting at most aRemPages additional pages. How many should we commit to
// amortise system calls?
size_t ExtraCommitPages(size_t aReqPages, size_t aRemainingPages)
MOZ_REQUIRES(mLock);
#endif
enum PurgeResult {
// The stop threshold of dirty pages was reached.
Done,
// There's more chunks in this arena that could be purged.
Continue,
// The only chunks with dirty pages are busy being purged by other threads.
Busy,
// The arena needs to be destroyed by the caller.
Dying,
};
// Purge some dirty pages.
//
// When this is called the caller has already tested ShouldStartPurge()
// (possibly on another thread asychronously) or is passing
// PurgeUnconditional. However because it's called without the lock it will
// recheck ShouldContinuePurge() before doing any work.
//
// It may purge a number of runs within a single chunk before returning. It
// will return Continue if there's more work to do in other chunks
// (ShouldContinuePurge()).
//
// To release more pages from other chunks then it's best to call Purge
// in a loop, looping when it returns Continue.
//
// This must be called without the mLock held (it'll take the lock).
//
PurgeResult Purge(PurgeCondition aCond) MOZ_EXCLUDES(mLock);
class PurgeInfo {
private:
size_t mDirtyInd = 0;
size_t mDirtyNPages = 0;
size_t mFreeRunInd = 0;
size_t mFreeRunLen = 0;
public:
arena_t& mArena;
arena_chunk_t* mChunk = nullptr;
size_t FreeRunLenBytes() const { return mFreeRunLen << gPageSize2Pow; }
// The last index of the free run.
size_t FreeRunLastInd() const { return mFreeRunInd + mFreeRunLen - 1; }
void* DirtyPtr() const {
return (void*)(uintptr_t(mChunk) + (mDirtyInd << gPageSize2Pow));
}
size_t DirtyLenBytes() const { return mDirtyNPages << gPageSize2Pow; }
// Purging memory is seperated into 3 phases.
// * FindDirtyPages() which find the dirty pages in a chunk and marks the
// run and chunk as busy while holding the lock.
// * Release the pages (without the lock)
// * UpdatePagesAndCounts() which marks the dirty pages as not-dirty and
// updates other counters (while holding the lock).
//
// FindDirtyPages() will return false purging should not continue purging in
// this chunk. Either because it has no dirty pages or is dying.
bool FindDirtyPages(bool aPurgedOnce) MOZ_REQUIRES(mArena.mLock);
// Returns a pair, the first field indicates if there are more dirty pages
// remaining in the current chunk. The second field if non-null points to a
// chunk that must be released by the caller.
std::pair<bool, arena_chunk_t*> UpdatePagesAndCounts()
MOZ_REQUIRES(mArena.mLock);
// FinishPurgingInChunk() is used whenever we decide to stop purging in a
// chunk, This could be because there are no more dirty pages, or the chunk
// is dying, or we hit the arena-level threshold.
void FinishPurgingInChunk(bool aAddToMAdvised) MOZ_REQUIRES(mArena.mLock);
explicit PurgeInfo(arena_t& arena, arena_chunk_t* chunk)
: mArena(arena), mChunk(chunk) {}
};
void HardPurge();
// Check mNumDirty against EffectiveMaxDirty and return the appropriate
// action to be taken by MayDoOrQueuePurge (outside mLock's scope).
//
// None: Nothing to do.
// PurgeNow: Immediate synchronous purge.
// Queue: Add a new purge request.
//
// Note that in the case of deferred purge this function takes into account
// mIsDeferredPurgeNeeded to avoid useless operations on the purge list
// that would require gArenas.mPurgeListLock.
inline purge_action_t ShouldStartPurge() MOZ_REQUIRES(mLock);
// Take action according to ShouldStartPurge.
inline void MayDoOrQueuePurge(purge_action_t aAction) MOZ_EXCLUDES(mLock);
// Check the EffectiveHalfMaxDirty threshold to decide if we continue purge.
// This threshold is lower than ShouldStartPurge to have some hysteresis.
bool ShouldContinuePurge(PurgeCondition aCond) MOZ_REQUIRES(mLock) {
return (mNumDirty > ((aCond == PurgeUnconditional) ? 0 : mMaxDirty >> 1));
}
// Update the last significant reuse timestamp.
void NotifySignificantReuse() MOZ_EXCLUDES(mLock);
bool IsMainThreadOnly() const { return !mLock.LockIsEnabled(); }
void* operator new(size_t aCount) = delete;
void* operator new(size_t aCount, const fallible_t&) noexcept;
void operator delete(void*);
};
namespace mozilla {
template <>
struct GetDoublyLinkedListElement<arena_t> {
static DoublyLinkedListElement<arena_t>& Get(arena_t* aThis) {
return aThis->mPurgeListElem;
}
};
} // namespace mozilla
struct ArenaTreeTrait {
static RedBlackTreeNode<arena_t>& GetTreeNode(arena_t* aThis) {
return aThis->mLink;
}
static inline Order Compare(arena_t* aNode, arena_t* aOther) {
MOZ_ASSERT(aNode);
MOZ_ASSERT(aOther);
return CompareInt(aNode->mId, aOther->mId);
}
};
// Bookkeeping for all the arenas used by the allocator.
// Arenas are separated in two categories:
// - "private" arenas, used through the moz_arena_* API
// - all the other arenas: the default arena, and thread-local arenas,
// used by the standard API.
class ArenaCollection {
public:
bool Init() MOZ_REQUIRES(gInitLock) MOZ_EXCLUDES(mLock) {
MOZ_PUSH_IGNORE_THREAD_SAFETY
mArenas.Init();
mPrivateArenas.Init();
#ifndef NON_RANDOM_ARENA_IDS
mMainThreadArenas.Init();
#endif
MOZ_POP_THREAD_SAFETY
arena_params_t params;
// The main arena allows more dirty pages than the default for other arenas.
params.mMaxDirty = opt_dirty_max;
mDefaultArena =
mLock.Init() ? CreateArena(/* aIsPrivate = */ false, &params) : nullptr;
mPurgeListLock.Init();
mIsDeferredPurgeEnabled = false;
return bool(mDefaultArena);
}
// The requested arena must exist.
inline arena_t* GetById(arena_id_t aArenaId, bool aIsPrivate)
MOZ_EXCLUDES(mLock);
arena_t* CreateArena(bool aIsPrivate, arena_params_t* aParams)
MOZ_EXCLUDES(mLock);
void DisposeArena(arena_t* aArena) MOZ_EXCLUDES(mLock) {
// This will not call MayPurge but only unlink the element in case.
// It returns true if we successfully removed the item from the list,
// meaning we have exclusive access to it and can delete it.
bool delete_now = RemoveFromOutstandingPurges(aArena);
{
MutexAutoLock lock(mLock);
Tree& tree =
#ifndef NON_RANDOM_ARENA_IDS
aArena->IsMainThreadOnly() ? mMainThreadArenas :
#endif
mPrivateArenas;
MOZ_RELEASE_ASSERT(tree.Search(aArena), "Arena not in tree");
tree.Remove(aArena);
mNumOperationsDisposedArenas += aArena->Operations();
}
{
MutexAutoLock lock(aArena->mLock);
if (!aArena->mIsPurgePending) {
// If no purge was pending then we have exclusive access to the
// arena and must delete it.
delete_now = true;
} else if (!delete_now) {
// The remaining possibility, when we failed to remove the arena from
// the list (because a purging thread alredy did so) then that thread
// will be the last thread holding the arena and is now responsible for
// deleting it.
aArena->mMustDeleteAfterPurge = true;
// Not that it's not possible to have checked the list of pending purges
// BEFORE the arena was added to the list because that would mean that
// an operation on the arena (free or realloc) was running concurrently
// with deletion, which would be a memory error and the assertions in
// the destructor help check for that.
}
}
if (delete_now) {
delete aArena;
}
}
void SetDefaultMaxDirtyPageModifier(int32_t aModifier) {
{
MutexAutoLock lock(mLock);
mDefaultMaxDirtyPageModifier = aModifier;
for (auto* arena : iter()) {
// We can only update max-dirty for main-thread-only arenas from the
// main thread.
if (!arena->IsMainThreadOnly() || IsOnMainThreadWeak()) {
arena->UpdateMaxDirty();
}
}
}
}
int32_t DefaultMaxDirtyPageModifier() { return mDefaultMaxDirtyPageModifier; }
using Tree = RedBlackTree<arena_t, ArenaTreeTrait>;
struct Iterator : Tree::Iterator {
explicit Iterator(Tree* aTree, Tree* aSecondTree,
Tree* aThirdTree = nullptr)
: Tree::Iterator(aTree),
mSecondTree(aSecondTree),
mThirdTree(aThirdTree) {}
Item<Iterator> begin() {
return Item<Iterator>(this, *Tree::Iterator::begin());
}
Item<Iterator> end() { return Item<Iterator>(this, nullptr); }
arena_t* Next() {
arena_t* result = Tree::Iterator::Next();
if (!result && mSecondTree) {
new (this) Iterator(mSecondTree, mThirdTree);
result = *Tree::Iterator::begin();
}
return result;
}
private:
Tree* mSecondTree;
Tree* mThirdTree;
};
Iterator iter() MOZ_REQUIRES(mLock) {
#ifdef NON_RANDOM_ARENA_IDS
return Iterator(&mArenas, &mPrivateArenas);
#else
return Iterator(&mArenas, &mPrivateArenas, &mMainThreadArenas);
#endif
}
inline arena_t* GetDefault() { return mDefaultArena; }
// Guards the collection of arenas. Must not be acquired while holding
// a single arena's lock or mPurgeListLock.
Mutex mLock MOZ_UNANNOTATED;
// Guards only the list of outstanding purge requests. Can be acquired
// while holding gArenas.mLock, but must not be acquired or held while
// holding or acquiring a single arena's lock.
Mutex mPurgeListLock;
// We're running on the main thread which is set by a call to SetMainThread().
bool IsOnMainThread() const {
return mMainThreadId.isSome() &&
ThreadIdEqual(mMainThreadId.value(), GetThreadId());
}
// We're running on the main thread or SetMainThread() has never been called.
bool IsOnMainThreadWeak() const {
return mMainThreadId.isNothing() || IsOnMainThread();
}
// After a fork set the new thread ID in the child.
// This is done as the first thing after a fork, before mLock even re-inits.
void ResetMainThread() MOZ_EXCLUDES(mLock) {
// The post fork handler in the child can run from a MacOS worker thread,
// so we can't set our main thread to it here. Instead we have to clear it.
mMainThreadId = Nothing();
}
void SetMainThread() MOZ_EXCLUDES(mLock) {
MutexAutoLock lock(mLock);
MOZ_ASSERT(mMainThreadId.isNothing());
mMainThreadId = Some(GetThreadId());
}
// This requires the lock to get a consistent count across all the active
// + disposed arenas.
uint64_t OperationsDisposedArenas() MOZ_REQUIRES(mLock) {
return mNumOperationsDisposedArenas;
}
// Enable or disable the lazy purge.
//
// Returns the former state of enablement.
// This is a global setting for all arenas. Changing it may cause an
// immediate purge for all arenas.
bool SetDeferredPurge(bool aEnable) {
MOZ_ASSERT(IsOnMainThreadWeak());
bool ret = mIsDeferredPurgeEnabled;
{
MutexAutoLock lock(mLock);
mIsDeferredPurgeEnabled = aEnable;
for (auto* arena : iter()) {
MaybeMutexAutoLock lock(arena->mLock);
arena->mIsDeferredPurgeEnabled = aEnable;
}
}
if (ret != aEnable) {
MayPurgeAll(PurgeIfThreshold);
}
return ret;
}
bool IsDeferredPurgeEnabled() { return mIsDeferredPurgeEnabled; }
// Set aside a new purge request for aArena.
void AddToOutstandingPurges(arena_t* aArena) MOZ_EXCLUDES(mPurgeListLock);
// Remove an unhandled purge request for aArena. Returns true if the arena
// was in the list.
bool RemoveFromOutstandingPurges(arena_t* aArena)
MOZ_EXCLUDES(mPurgeListLock);
// Execute all outstanding purge requests, if any.
void MayPurgeAll(PurgeCondition aCond);
// Purge some dirty memory, based on purge requests, returns true if there are
// more to process.
//
// Returns a purge_result_t with the following meaning:
// Done: Purge has completed for all arenas.
// NeedsMore: There may be some arenas that needs to be purged now.
// WantsLater: There is at least one arena that might want a purge later,
// according to aReuseGraceMS.
//
// Parameters:
// aPeekOnly: If true, check only if there is work to do without doing it.
// aReuseGraceMS: The time to wait with purge after a
// significant re-use happened for an arena.
// aKeepGoing: If this returns false purging will cease.
//
// This could exit for 3 different reasons.
// - There are no more requests (it returns false)
// - There are more requests but aKeepGoing() returned false. (returns true)
// - One arena is completely purged, (returns true).
//
purge_result_t MayPurgeSteps(bool aPeekOnly, uint32_t aReuseGraceMS,
const Maybe<std::function<bool()>>& aKeepGoing);
private:
const static arena_id_t MAIN_THREAD_ARENA_BIT = 0x1;
#ifndef NON_RANDOM_ARENA_IDS
// Can be called with or without lock, depending on aTree.
inline arena_t* GetByIdInternal(Tree& aTree, arena_id_t aArenaId);
arena_id_t MakeRandArenaId(bool aIsMainThreadOnly) const MOZ_REQUIRES(mLock);
#endif
static bool ArenaIdIsMainThreadOnly(arena_id_t aArenaId) {
return aArenaId & MAIN_THREAD_ARENA_BIT;
}
arena_t* mDefaultArena;
arena_id_t mLastPublicArenaId MOZ_GUARDED_BY(mLock);
// Accessing mArenas and mPrivateArenas can only be done while holding mLock.
Tree mArenas MOZ_GUARDED_BY(mLock);
Tree mPrivateArenas MOZ_GUARDED_BY(mLock);
#ifdef NON_RANDOM_ARENA_IDS
// Arena ids are pseudo-obfuscated/deobfuscated based on these values randomly
// initialized on first use.
arena_id_t mArenaIdKey = 0;
int8_t mArenaIdRotation = 0;
#else
// Some mMainThreadArenas accesses to mMainThreadArenas can (and should) elude
// the lock, see GetById().
Tree mMainThreadArenas MOZ_GUARDED_BY(mLock);
#endif
// Set only rarely and then propagated on the same thread to all arenas via
// UpdateMaxDirty(). But also read in ExtraCommitPages on arbitrary threads.
// TODO: Could ExtraCommitPages use arena_t::mMaxDirty instead ?
Atomic<int32_t> mDefaultMaxDirtyPageModifier;
// This is never changed except for forking, and it does not need mLock.
Maybe<ThreadId> mMainThreadId;
// The number of operations that happened in arenas that have since been
// destroyed.
uint64_t mNumOperationsDisposedArenas = 0;
// Linked list of outstanding purges. This list has no particular order.
// It is ok for an arena to be in this list even if mIsPurgePending is false,
// it will just cause an extra round of a (most likely no-op) purge.
// It is not ok to not be in this list but have mIsPurgePending set to true,
// as this would prevent any future purges for this arena (except for during
// MayPurgeStep or Purge).
DoublyLinkedList<arena_t> mOutstandingPurges MOZ_GUARDED_BY(mPurgeListLock);
// Flag if we should defer purge to later. Only ever set when holding the
// collection lock. Read only during arena_t ctor.
Atomic<bool> mIsDeferredPurgeEnabled;
};
MOZ_RUNINIT static ArenaCollection gArenas;
// ******
// Chunks.
static AddressRadixTree<(sizeof(void*) << 3) - LOG2(kChunkSize)> gChunkRTree;
// Protects chunk-related data structures.
static Mutex chunks_mtx;
// Trees of chunks that were previously allocated (trees differ only in node
// ordering). These are used when allocating chunks, in an attempt to re-use
// address space. Depending on function, different tree orderings are needed,
// which is why there are two trees with the same contents.
static RedBlackTree<extent_node_t, ExtentTreeSzTrait> gChunksBySize
MOZ_GUARDED_BY(chunks_mtx);
static RedBlackTree<extent_node_t, ExtentTreeTrait> gChunksByAddress
MOZ_GUARDED_BY(chunks_mtx);
// Protects huge allocation-related data structures.
static Mutex huge_mtx;
// Tree of chunks that are stand-alone huge allocations.
static RedBlackTree<extent_node_t, ExtentTreeTrait> huge
MOZ_GUARDED_BY(huge_mtx);
// Huge allocation statistics.
static size_t huge_allocated MOZ_GUARDED_BY(huge_mtx);
static size_t huge_mapped MOZ_GUARDED_BY(huge_mtx);
static uint64_t huge_operations MOZ_GUARDED_BY(huge_mtx);
// **************************
// base (internal allocation).
static Mutex base_mtx;
// Current pages that are being used for internal memory allocations. These
// pages are carved up in cacheline-size quanta, so that there is no chance of
// false cache line sharing.
static void* base_pages MOZ_GUARDED_BY(base_mtx);
static void* base_next_addr MOZ_GUARDED_BY(base_mtx);
static void* base_next_decommitted MOZ_GUARDED_BY(base_mtx);
// Address immediately past base_pages.
static void* base_past_addr MOZ_GUARDED_BY(base_mtx);
static size_t base_mapped MOZ_GUARDED_BY(base_mtx);
static size_t base_committed MOZ_GUARDED_BY(base_mtx);
// ******
// Arenas.
// The arena associated with the current thread (per
// jemalloc_thread_local_arena) On OSX, __thread/thread_local circles back
// calling malloc to allocate storage on first access on each thread, which
// leads to an infinite loop, but pthread-based TLS somehow doesn't have this
// problem.
#if !defined(XP_DARWIN)
static MOZ_THREAD_LOCAL(arena_t*) thread_arena;
#else
static detail::ThreadLocal<arena_t*, detail::ThreadLocalKeyStorage>
thread_arena;
#endif
// *****************************
// Runtime configuration options.
#ifdef MALLOC_RUNTIME_CONFIG
# define MALLOC_RUNTIME_VAR static
#else
# define MALLOC_RUNTIME_VAR static const
#endif
enum PoisonType {
NONE,
SOME,
ALL,
};
MALLOC_RUNTIME_VAR bool opt_junk = false;
MALLOC_RUNTIME_VAR bool opt_zero = false;
#ifdef EARLY_BETA_OR_EARLIER
MALLOC_RUNTIME_VAR PoisonType opt_poison = ALL;
#else
MALLOC_RUNTIME_VAR PoisonType opt_poison = SOME;
#endif
// Keep this larger than and ideally a multiple of kCacheLineSize;
MALLOC_RUNTIME_VAR size_t opt_poison_size = 256;
#ifndef MALLOC_RUNTIME_CONFIG
static_assert(opt_poison_size >= kCacheLineSize);
static_assert((opt_poison_size % kCacheLineSize) == 0);
#endif
static bool opt_randomize_small = true;
// ***************************************************************************
// Begin forward declarations.
static void* chunk_alloc(size_t aSize, size_t aAlignment, bool aBase);
static void chunk_dealloc(void* aChunk, size_t aSize, ChunkType aType);
#ifdef MOZ_DEBUG
static void chunk_assert_zero(void* aPtr, size_t aSize);
#endif
static void huge_dalloc(void* aPtr, arena_t* aArena);
static bool malloc_init_hard();
#ifndef XP_WIN
# ifdef XP_DARWIN
# define FORK_HOOK extern "C"
# else
# define FORK_HOOK static
# endif
FORK_HOOK void _malloc_prefork(void);
FORK_HOOK void _malloc_postfork_parent(void);
FORK_HOOK void _malloc_postfork_child(void);
# ifdef XP_DARWIN
FORK_HOOK void _malloc_postfork(void);
# endif
#endif
// End forward declarations.
// ***************************************************************************
// FreeBSD's pthreads implementation calls malloc(3), so the malloc
// implementation has to take pains to avoid infinite recursion during
// initialization.
// Returns whether the allocator was successfully initialized.
static inline bool malloc_init() {
if (!malloc_initialized) {
return malloc_init_hard();
}
return true;
}
static void _malloc_message(const char* p) {
#if !defined(XP_WIN)
# define _write write
#endif
// Pretend to check _write() errors to suppress gcc warnings about
// warn_unused_result annotations in some versions of glibc headers.
if (_write(STDERR_FILENO, p, (unsigned int)strlen(p)) < 0) {
return;
}
}
template <typename... Args>
static void _malloc_message(const char* p, Args... args) {
_malloc_message(p);
_malloc_message(args...);
}
#ifdef ANDROID
// Android's pthread.h does not declare pthread_atfork() until SDK 21.
extern "C" MOZ_EXPORT int pthread_atfork(void (*)(void), void (*)(void),
void (*)(void));
#endif
// ***************************************************************************
// Begin Utility functions/macros.
// Return the chunk address for allocation address a.
static inline arena_chunk_t* GetChunkForPtr(const void* aPtr) {
return (arena_chunk_t*)(uintptr_t(aPtr) & ~kChunkSizeMask);
}
// Return the chunk offset of address a.
static inline size_t GetChunkOffsetForPtr(const void* aPtr) {
return (size_t)(uintptr_t(aPtr) & kChunkSizeMask);
}
static inline const char* _getprogname(void) { return "<jemalloc>"; }
static inline void MaybePoison(void* aPtr, size_t aSize) {
size_t size;
switch (opt_poison) {
case NONE:
return;
case SOME:
size = std::min(aSize, opt_poison_size);
break;
case ALL:
size = aSize;
break;
}
MOZ_ASSERT(size != 0 && size <= aSize);
memset(aPtr, kAllocPoison, size);
}
// Fill the given range of memory with zeroes or junk depending on opt_junk and
// opt_zero.
static inline void ApplyZeroOrJunk(void* aPtr, size_t aSize) {
if (opt_junk) {
memset(aPtr, kAllocJunk, aSize);
} else if (opt_zero) {
memset(aPtr, 0, aSize);
}
}
// On Windows, delay crashing on OOM.
#ifdef XP_WIN
// Implementation of VirtualAlloc wrapper (bug 1716727).
namespace MozAllocRetries {
// Maximum retry count on OOM.
constexpr size_t kMaxAttempts = 10;
// Minimum delay time between retries. (The actual delay time may be larger. See
// Microsoft's documentation for ::Sleep() for details.)
constexpr size_t kDelayMs = 50;
using StallSpecs = ::mozilla::StallSpecs;
static constexpr StallSpecs maxStall = {.maxAttempts = kMaxAttempts,
.delayMs = kDelayMs};
static inline StallSpecs GetStallSpecs() {
# if defined(JS_STANDALONE)
// GetGeckoProcessType() isn't available in this configuration. (SpiderMonkey
// on Windows mostly skips this in favor of directly calling ::VirtualAlloc(),
// though, so it's probably not going to matter whether we stall here or not.)
return maxStall;
# else
switch (GetGeckoProcessType()) {
// For the main process, stall for the maximum permissible time period. (The
// main process is the most important one to keep alive.)
case GeckoProcessType::GeckoProcessType_Default:
return maxStall;
// For all other process types, stall for at most half as long.
default:
return {.maxAttempts = maxStall.maxAttempts / 2,
.delayMs = maxStall.delayMs};
}
# endif
}
} // namespace MozAllocRetries
namespace mozilla {
StallSpecs GetAllocatorStallSpecs() {
return ::MozAllocRetries::GetStallSpecs();
}
// Drop-in wrapper around VirtualAlloc. When out of memory, may attempt to stall
// and retry rather than returning immediately, in hopes that the page file is
// about to be expanded by Windows.
//
// Ref:
// https://docs.microsoft.com/en-us/troubleshoot/windows-client/performance/slow-page-file-growth-memory-allocation-errors
void* MozVirtualAlloc(void* lpAddress, size_t dwSize, uint32_t flAllocationType,
uint32_t flProtect) {
using namespace MozAllocRetries;
DWORD const lastError = ::GetLastError();
constexpr auto IsOOMError = [] {
switch (::GetLastError()) {
// This is the usual error result from VirtualAlloc for OOM.
case ERROR_COMMITMENT_LIMIT:
// Although rare, this has also been observed in low-memory situations.
// (Presumably this means Windows can't allocate enough kernel-side space
// for its own internal representation of the process's virtual address
// space.)
case ERROR_NOT_ENOUGH_MEMORY:
return true;
}
return false;
};
{
void* ptr = ::VirtualAlloc(lpAddress, dwSize, flAllocationType, flProtect);
if (MOZ_LIKELY(ptr)) return ptr;
// We can't do anything for errors other than OOM...
if (!IsOOMError()) return nullptr;
// ... or if this wasn't a request to commit memory in the first place.
// (This function has no strategy for resolving MEM_RESERVE failures.)
if (!(flAllocationType & MEM_COMMIT)) return nullptr;
}
// Retry as many times as desired (possibly zero).
const StallSpecs stallSpecs = GetStallSpecs();
const auto ret =
stallSpecs.StallAndRetry(&::Sleep, [&]() -> std::optional<void*> {
void* ptr =
::VirtualAlloc(lpAddress, dwSize, flAllocationType, flProtect);
if (ptr) {
// The OOM status has been handled, and should not be reported to
// telemetry.
if (IsOOMError()) {
::SetLastError(lastError);
}
return ptr;
}
// Failure for some reason other than OOM.
if (!IsOOMError()) {
return nullptr;
}
return std::nullopt;
});
return ret.value_or(nullptr);
}
} // namespace mozilla
#endif // XP_WIN
// ***************************************************************************
static inline void pages_decommit(void* aAddr, size_t aSize) {
#ifdef XP_WIN
// The region starting at addr may have been allocated in multiple calls
// to VirtualAlloc and recycled, so decommitting the entire region in one
// go may not be valid. However, since we allocate at least a chunk at a
// time, we may touch any region in chunksized increments.
size_t pages_size = std::min(aSize, kChunkSize - GetChunkOffsetForPtr(aAddr));
while (aSize > 0) {
// This will cause Access Violation on read and write and thus act as a
// guard page or region as well.
if (!VirtualFree(aAddr, pages_size, MEM_DECOMMIT)) {
MOZ_CRASH();
}
aAddr = (void*)((uintptr_t)aAddr + pages_size);
aSize -= pages_size;
pages_size = std::min(aSize, kChunkSize);
}
#else
if (mmap(aAddr, aSize, PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1,
0) == MAP_FAILED) {
// We'd like to report the OOM for our tooling, but we can't allocate
// memory at this point, so avoid the use of printf.
const char out_of_mappings[] =
"[unhandlable oom] Failed to mmap, likely no more mappings "
"available " __FILE__ " : " MOZ_STRINGIFY(__LINE__);
if (errno == ENOMEM) {
# ifndef ANDROID
fputs(out_of_mappings, stderr);
fflush(stderr);
# endif
MOZ_CRASH_ANNOTATE(out_of_mappings);
}
MOZ_REALLY_CRASH(__LINE__);
}
MozTagAnonymousMemory(aAddr, aSize, "jemalloc-decommitted");
#endif
}
// Commit pages. Returns whether pages were committed.
[[nodiscard]] static inline bool pages_commit(void* aAddr, size_t aSize) {
#ifdef XP_WIN
// The region starting at addr may have been allocated in multiple calls
// to VirtualAlloc and recycled, so committing the entire region in one
// go may not be valid. However, since we allocate at least a chunk at a
// time, we may touch any region in chunksized increments.
size_t pages_size = std::min(aSize, kChunkSize - GetChunkOffsetForPtr(aAddr));
while (aSize > 0) {
if (!MozVirtualAlloc(aAddr, pages_size, MEM_COMMIT, PAGE_READWRITE)) {
return false;
}
aAddr = (void*)((uintptr_t)aAddr + pages_size);
aSize -= pages_size;
pages_size = std::min(aSize, kChunkSize);
}
#else
if (mmap(aAddr, aSize, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) == MAP_FAILED) {
return false;
}
MozTagAnonymousMemory(aAddr, aSize, "jemalloc");
#endif
return true;
}
// Initialize base allocation data structures.
static void base_init() MOZ_REQUIRES(gInitLock) {
base_mtx.Init();
MOZ_PUSH_IGNORE_THREAD_SAFETY
base_mapped = 0;
base_committed = 0;
MOZ_POP_THREAD_SAFETY
}
static bool base_pages_alloc(size_t minsize) MOZ_REQUIRES(base_mtx) {
size_t csize;
size_t pminsize;
MOZ_ASSERT(minsize != 0);
csize = CHUNK_CEILING(minsize);
base_pages = chunk_alloc(csize, kChunkSize, true);
if (!base_pages) {
return true;
}
base_next_addr = base_pages;
base_past_addr = (void*)((uintptr_t)base_pages + csize);
// Leave enough pages for minsize committed, since otherwise they would
// have to be immediately recommitted.
pminsize = PAGE_CEILING(minsize);
base_next_decommitted = (void*)((uintptr_t)base_pages + pminsize);
if (pminsize < csize) {
pages_decommit(base_next_decommitted, csize - pminsize);
}
base_mapped += csize;
base_committed += pminsize;
return false;
}
static void* base_alloc(size_t aSize) {
void* ret;
size_t csize;
// Round size up to nearest multiple of the cacheline size.
csize = CACHELINE_CEILING(aSize);
MutexAutoLock lock(base_mtx);
// Make sure there's enough space for the allocation.
if ((uintptr_t)base_next_addr + csize > (uintptr_t)base_past_addr) {
if (base_pages_alloc(csize)) {
return nullptr;
}
}
// Allocate.
ret = base_next_addr;
base_next_addr = (void*)((uintptr_t)base_next_addr + csize);
// Make sure enough pages are committed for the new allocation.
if ((uintptr_t)base_next_addr > (uintptr_t)base_next_decommitted) {
void* pbase_next_addr = (void*)(PAGE_CEILING((uintptr_t)base_next_addr));
if (!pages_commit(
base_next_decommitted,
(uintptr_t)pbase_next_addr - (uintptr_t)base_next_decommitted)) {
return nullptr;
}
base_committed +=
(uintptr_t)pbase_next_addr - (uintptr_t)base_next_decommitted;
base_next_decommitted = pbase_next_addr;
}
return ret;
}
static void* base_calloc(size_t aNumber, size_t aSize) {
void* ret = base_alloc(aNumber * aSize);
if (ret) {
memset(ret, 0, aNumber * aSize);
}
return ret;
}
// A specialization of the base allocator with a free list.
template <typename T>
struct TypedBaseAlloc {
static T* sFirstFree;
static size_t size_of() { return sizeof(T); }
static T* alloc() {
T* ret;
base_mtx.Lock();
if (sFirstFree) {
ret = sFirstFree;
sFirstFree = *(T**)ret;
base_mtx.Unlock();
} else {
base_mtx.Unlock();
ret = (T*)base_alloc(size_of());
}
return ret;
}
static void dealloc(T* aNode) {
MutexAutoLock lock(base_mtx);
*(T**)aNode = sFirstFree;
sFirstFree = aNode;
}
};
using ExtentAlloc = TypedBaseAlloc<extent_node_t>;
template <>
extent_node_t* ExtentAlloc::sFirstFree = nullptr;
template <>
arena_t* TypedBaseAlloc<arena_t>::sFirstFree = nullptr;
template <>
size_t TypedBaseAlloc<arena_t>::size_of() {
// Allocate enough space for trailing bins.
return sizeof(arena_t) + (sizeof(arena_bin_t) * NUM_SMALL_CLASSES);
}
template <typename T>
struct BaseAllocFreePolicy {
void operator()(T* aPtr) { TypedBaseAlloc<T>::dealloc(aPtr); }
};
using UniqueBaseNode =
UniquePtr<extent_node_t, BaseAllocFreePolicy<extent_node_t>>;
// End Utility functions/macros.
// ***************************************************************************
// Begin chunk management functions.
#ifdef XP_WIN
static void* pages_map(void* aAddr, size_t aSize) {
void* ret = nullptr;
ret = MozVirtualAlloc(aAddr, aSize, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
return ret;
}
static void pages_unmap(void* aAddr, size_t aSize) {
if (VirtualFree(aAddr, 0, MEM_RELEASE) == 0) {
_malloc_message(_getprogname(), ": (malloc) Error in VirtualFree()\n");
}
}
#else
static void pages_unmap(void* aAddr, size_t aSize) {
if (munmap(aAddr, aSize) == -1) {
char buf[64];
if (strerror_r(errno, buf, sizeof(buf)) == 0) {
_malloc_message(_getprogname(), ": (malloc) Error in munmap(): ", buf,
"\n");
}
}
}
static void* pages_map(void* aAddr, size_t aSize) {
void* ret;
# if defined(__ia64__) || \
(defined(__sparc__) && defined(__arch64__) && defined(__linux__))
// The JS engine assumes that all allocated pointers have their high 17 bits
// clear, which ia64's mmap doesn't support directly. However, we can emulate
// it by passing mmap an "addr" parameter with those bits clear. The mmap will
// return that address, or the nearest available memory above that address,
// providing a near-guarantee that those bits are clear. If they are not, we
// return nullptr below to indicate out-of-memory.
//
// The addr is chosen as 0x0000070000000000, which still allows about 120TB of
// virtual address space.
//
// See Bug 589735 for more information.
bool check_placement = true;
if (!aAddr) {
aAddr = (void*)0x0000070000000000;
check_placement = false;
}
# endif
# if defined(__sparc__) && defined(__arch64__) && defined(__linux__)
const uintptr_t start = 0x0000070000000000ULL;
const uintptr_t end = 0x0000800000000000ULL;
// Copied from js/src/gc/Memory.cpp and adapted for this source
uintptr_t hint;
void* region = MAP_FAILED;
for (hint = start; region == MAP_FAILED && hint + aSize <= end;
hint += kChunkSize) {
region = mmap((void*)hint, aSize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON, -1, 0);
if (region != MAP_FAILED) {
if (((size_t)region + (aSize - 1)) & 0xffff800000000000) {
if (munmap(region, aSize)) {
MOZ_ASSERT(errno == ENOMEM);
}
region = MAP_FAILED;
}
}
}
ret = region;
# else
// We don't use MAP_FIXED here, because it can cause the *replacement*
// of existing mappings, and we only want to create new mappings.
ret =
mmap(aAddr, aSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
MOZ_ASSERT(ret);
# endif
if (ret == MAP_FAILED) {
ret = nullptr;
}
# if defined(__ia64__) || \
(defined(__sparc__) && defined(__arch64__) && defined(__linux__))
// If the allocated memory doesn't have its upper 17 bits clear, consider it
// as out of memory.
else if ((long long)ret & 0xffff800000000000) {
munmap(ret, aSize);
ret = nullptr;
}
// If the caller requested a specific memory location, verify that's what mmap
// returned.
else if (check_placement && ret != aAddr) {
# else
else if (aAddr && ret != aAddr) {
# endif
// We succeeded in mapping memory, but not in the right place.
pages_unmap(ret, aSize);
ret = nullptr;
}
if (ret) {
MozTagAnonymousMemory(ret, aSize, "jemalloc");
}
# if defined(__ia64__) || \
(defined(__sparc__) && defined(__arch64__) && defined(__linux__))
MOZ_ASSERT(!ret || (!check_placement && ret) ||
(check_placement && ret == aAddr));
# else
MOZ_ASSERT(!ret || (!aAddr && ret != aAddr) || (aAddr && ret == aAddr));
# endif
return ret;
}
#endif
#ifdef XP_DARWIN
# define VM_COPY_MIN kChunkSize
static inline void pages_copy(void* dest, const void* src, size_t n) {
MOZ_ASSERT((void*)((uintptr_t)dest & ~gPageSizeMask) == dest);
MOZ_ASSERT(n >= VM_COPY_MIN);
MOZ_ASSERT((void*)((uintptr_t)src & ~gPageSizeMask) == src);
kern_return_t r = vm_copy(mach_task_self(), (vm_address_t)src, (vm_size_t)n,
(vm_address_t)dest);
if (r != KERN_SUCCESS) {
MOZ_CRASH("vm_copy() failed");
}
}
#endif
template <size_t Bits>
bool AddressRadixTree<Bits>::Init() {
mLock.Init();
mRoot = (void**)base_calloc(1 << kBitsAtLevel1, sizeof(void*));
return mRoot;
}
template <size_t Bits>
void** AddressRadixTree<Bits>::GetSlotInternal(void* aAddr, bool aCreate) {
uintptr_t key = reinterpret_cast<uintptr_t>(aAddr);
uintptr_t subkey;
unsigned i, lshift, height, bits;
void** node;
void** child;
for (i = lshift = 0, height = kHeight, node = mRoot; i < height - 1;
i++, lshift += bits, node = child) {
bits = i ? kBitsPerLevel : kBitsAtLevel1;
subkey = (key << lshift) >> ((sizeof(void*) << 3) - bits);
child = (void**)node[subkey];
if (!child && aCreate) {
child = (void**)base_calloc(1 << kBitsPerLevel, sizeof(void*));
if (child) {
node[subkey] = child;
}
}
if (!child) {
return nullptr;
}
}
// node is a leaf, so it contains values rather than node
// pointers.
bits = i ? kBitsPerLevel : kBitsAtLevel1;
subkey = (key << lshift) >> ((sizeof(void*) << 3) - bits);
return &node[subkey];
}
template <size_t Bits>
void* AddressRadixTree<Bits>::Get(void* aAddr) {
void* ret = nullptr;
void** slot = GetSlotIfExists(aAddr);
if (slot) {
ret = *slot;
}
#ifdef MOZ_DEBUG
MutexAutoLock lock(mLock);
// Suppose that it were possible for a jemalloc-allocated chunk to be
// munmap()ped, followed by a different allocator in another thread re-using
// overlapping virtual memory, all without invalidating the cached rtree
// value. The result would be a false positive (the rtree would claim that
// jemalloc owns memory that it had actually discarded). I don't think this
// scenario is possible, but the following assertion is a prudent sanity
// check.
if (!slot) {
// In case a slot has been created in the meantime.
slot = GetSlotInternal(aAddr, false);
}
if (slot) {
// The MutexAutoLock above should act as a memory barrier, forcing
// the compiler to emit a new read instruction for *slot.
MOZ_ASSERT(ret == *slot);
} else {
MOZ_ASSERT(ret == nullptr);
}
#endif
return ret;
}
template <size_t Bits>
bool AddressRadixTree<Bits>::Set(void* aAddr, void* aValue) {
MutexAutoLock lock(mLock);
void** slot = GetOrCreateSlot(aAddr);
if (slot) {
*slot = aValue;
}
return slot;
}
// pages_trim, chunk_alloc_mmap_slow and chunk_alloc_mmap were cherry-picked
// from upstream jemalloc 3.4.1 to fix Mozilla bug 956501.
// Return the offset between a and the nearest aligned address at or below a.
#define ALIGNMENT_ADDR2OFFSET(a, alignment) \
((size_t)((uintptr_t)(a) & ((alignment) - 1)))
// Return the smallest alignment multiple that is >= s.
#define ALIGNMENT_CEILING(s, alignment) \
(((s) + ((alignment) - 1)) & (~((alignment) - 1)))
static void* pages_trim(void* addr, size_t alloc_size, size_t leadsize,
size_t size) {
void* ret = (void*)((uintptr_t)addr + leadsize);
MOZ_ASSERT(alloc_size >= leadsize + size);
#ifdef XP_WIN
{
void* new_addr;
pages_unmap(addr, alloc_size);
new_addr = pages_map(ret, size);
if (new_addr == ret) {
return ret;
}
if (new_addr) {
pages_unmap(new_addr, size);
}
return nullptr;
}
#else
{
size_t trailsize = alloc_size - leadsize - size;
if (leadsize != 0) {
pages_unmap(addr, leadsize);
}
if (trailsize != 0) {
pages_unmap((void*)((uintptr_t)ret + size), trailsize);
}
return ret;
}
#endif
}
static void* chunk_alloc_mmap_slow(size_t size, size_t alignment) {
void *ret, *pages;
size_t alloc_size, leadsize;
alloc_size = size + alignment - gRealPageSize;
// Beware size_t wrap-around.
if (alloc_size < size) {
return nullptr;
}
do {
pages = pages_map(nullptr, alloc_size);
if (!pages) {
return nullptr;
}
leadsize =
ALIGNMENT_CEILING((uintptr_t)pages, alignment) - (uintptr_t)pages;
ret = pages_trim(pages, alloc_size, leadsize, size);
} while (!ret);
MOZ_ASSERT(ret);
return ret;
}
static void* chunk_alloc_mmap(size_t size, size_t alignment) {
void* ret;
size_t offset;
// Ideally, there would be a way to specify alignment to mmap() (like
// NetBSD has), but in the absence of such a feature, we have to work
// hard to efficiently create aligned mappings. The reliable, but
// slow method is to create a mapping that is over-sized, then trim the
// excess. However, that always results in one or two calls to
// pages_unmap().
//
// Optimistically try mapping precisely the right amount before falling
// back to the slow method, with the expectation that the optimistic
// approach works most of the time.
ret = pages_map(nullptr, size);
if (!ret) {
return nullptr;
}
offset = ALIGNMENT_ADDR2OFFSET(ret, alignment);
if (offset != 0) {
pages_unmap(ret, size);
return chunk_alloc_mmap_slow(size, alignment);
}
MOZ_ASSERT(ret);
return ret;
}
// Purge and release the pages in the chunk of length `length` at `addr` to
// the OS.
// Returns whether the pages are guaranteed to be full of zeroes when the
// function returns.
// The force_zero argument explicitly requests that the memory is guaranteed
// to be full of zeroes when the function returns.
static bool pages_purge(void* addr, size_t length, bool force_zero) {
pages_decommit(addr, length);
return true;
}
static void* chunk_recycle(size_t aSize, size_t aAlignment) {
extent_node_t key;
size_t alloc_size = aSize + aAlignment - kChunkSize;
// Beware size_t wrap-around.
if (alloc_size < aSize) {
return nullptr;
}
key.mAddr = nullptr;
key.mSize = alloc_size;
chunks_mtx.Lock();
extent_node_t* node = gChunksBySize.SearchOrNext(&key);
if (!node) {
chunks_mtx.Unlock();
return nullptr;
}
size_t leadsize = ALIGNMENT_CEILING((uintptr_t)node->mAddr, aAlignment) -
(uintptr_t)node->mAddr;
MOZ_ASSERT(node->mSize >= leadsize + aSize);
size_t trailsize = node->mSize - leadsize - aSize;
void* ret = (void*)((uintptr_t)node->mAddr + leadsize);
// All recycled chunks are zeroed (because they're purged) before being
// recycled.
MOZ_ASSERT(node->mChunkType == ZEROED_CHUNK);
// Remove node from the tree.
gChunksBySize.Remove(node);
gChunksByAddress.Remove(node);
if (leadsize != 0) {
// Insert the leading space as a smaller chunk.
node->mSize = leadsize;
gChunksBySize.Insert(node);
gChunksByAddress.Insert(node);
node = nullptr;
}
if (trailsize != 0) {
// Insert the trailing space as a smaller chunk.
if (!node) {
// An additional node is required, but
// TypedBaseAlloc::alloc() can cause a new base chunk to be
// allocated. Drop chunks_mtx in order to avoid
// deadlock, and if node allocation fails, deallocate
// the result before returning an error.
chunks_mtx.Unlock();
node = ExtentAlloc::alloc();
if (!node) {
chunk_dealloc(ret, aSize, ZEROED_CHUNK);
return nullptr;
}
chunks_mtx.Lock();
}
node->mAddr = (void*)((uintptr_t)(ret) + aSize);
node->mSize = trailsize;
node->mChunkType = ZEROED_CHUNK;
gChunksBySize.Insert(node);
gChunksByAddress.Insert(node);
node = nullptr;
}
gRecycledSize -= aSize;
chunks_mtx.Unlock();
if (node) {
ExtentAlloc::dealloc(node);
}
if (!pages_commit(ret, aSize)) {
return nullptr;
}
return ret;
}
static void chunks_init() MOZ_REQUIRES(gInitLock) {
// Initialize chunks data.
chunks_mtx.Init();
MOZ_PUSH_IGNORE_THREAD_SAFETY
gChunksBySize.Init();
gChunksByAddress.Init();
MOZ_POP_THREAD_SAFETY
}
#ifdef XP_WIN
// On Windows, calls to VirtualAlloc and VirtualFree must be matched, making it
// awkward to recycle allocations of varying sizes. Therefore we only allow
// recycling when the size equals the chunksize, unless deallocation is entirely
// disabled.
# define CAN_RECYCLE(size) ((size) == kChunkSize)
#else
# define CAN_RECYCLE(size) true
#endif
// Allocates `size` bytes of system memory aligned for `alignment`.
// `base` indicates whether the memory will be used for the base allocator
// (e.g. base_alloc).
// `zeroed` is an outvalue that returns whether the allocated memory is
// guaranteed to be full of zeroes. It can be omitted when the caller doesn't
// care about the result.
static void* chunk_alloc(size_t aSize, size_t aAlignment, bool aBase) {
void* ret = nullptr;
MOZ_ASSERT(aSize != 0);
MOZ_ASSERT((aSize & kChunkSizeMask) == 0);
MOZ_ASSERT(aAlignment != 0);
MOZ_ASSERT((aAlignment & kChunkSizeMask) == 0);
// Base allocations can't be fulfilled by recycling because of
// possible deadlock or infinite recursion.
if (CAN_RECYCLE(aSize) && !aBase) {
ret = chunk_recycle(aSize, aAlignment);
}
if (!ret) {
ret = chunk_alloc_mmap(aSize, aAlignment);
}
if (ret && !aBase) {
if (!gChunkRTree.Set(ret, ret)) {
chunk_dealloc(ret, aSize, UNKNOWN_CHUNK);
return nullptr;
}
}
MOZ_ASSERT(GetChunkOffsetForPtr(ret) == 0);
return ret;
}
#ifdef MOZ_DEBUG
static void chunk_assert_zero(void* aPtr, size_t aSize) {
// Only run this expensive check in a vigilant mode.
# ifdef MALLOC_DEBUG_VIGILANT
size_t i;
size_t* p = (size_t*)(uintptr_t)aPtr;
for (i = 0; i < aSize / sizeof(size_t); i++) {
MOZ_ASSERT(p[i] == 0);
}
# endif
}
#endif
static void chunk_record(void* aChunk, size_t aSize, ChunkType aType) {
extent_node_t key;
if (aType != ZEROED_CHUNK) {
if (pages_purge(aChunk, aSize, aType == HUGE_CHUNK)) {
aType = ZEROED_CHUNK;
}
}
// Allocate a node before acquiring chunks_mtx even though it might not
// be needed, because TypedBaseAlloc::alloc() may cause a new base chunk to
// be allocated, which could cause deadlock if chunks_mtx were already
// held.
UniqueBaseNode xnode(ExtentAlloc::alloc());
// Use xprev to implement conditional deferred deallocation of prev.
UniqueBaseNode xprev;
// RAII deallocates xnode and xprev defined above after unlocking
// in order to avoid potential dead-locks
MutexAutoLock lock(chunks_mtx);
key.mAddr = (void*)((uintptr_t)aChunk + aSize);
extent_node_t* node = gChunksByAddress.SearchOrNext(&key);
// Try to coalesce forward.
if (node && node->mAddr == key.mAddr) {
// Coalesce chunk with the following address range. This does
// not change the position within gChunksByAddress, so only
// remove/insert from/into gChunksBySize.
gChunksBySize.Remove(node);
node->mAddr = aChunk;
node->mSize += aSize;
if (node->mChunkType != aType) {
node->mChunkType = RECYCLED_CHUNK;
}
gChunksBySize.Insert(node);
} else {
// Coalescing forward failed, so insert a new node.
if (!xnode) {
// TypedBaseAlloc::alloc() failed, which is an exceedingly
// unlikely failure. Leak chunk; its pages have
// already been purged, so this is only a virtual
// memory leak.
return;
}
node = xnode.release();
node->mAddr = aChunk;
node->mSize = aSize;
node->mChunkType = aType;
gChunksByAddress.Insert(node);
gChunksBySize.Insert(node);
}
// Try to coalesce backward.
extent_node_t* prev = gChunksByAddress.Prev(node);
if (prev && (void*)((uintptr_t)prev->mAddr + prev->mSize) == aChunk) {
// Coalesce chunk with the previous address range. This does
// not change the position within gChunksByAddress, so only
// remove/insert node from/into gChunksBySize.
gChunksBySize.Remove(prev);
gChunksByAddress.Remove(prev);
gChunksBySize.Remove(node);
node->mAddr = prev->mAddr;
node->mSize += prev->mSize;
if (node->mChunkType != prev->mChunkType) {
node->mChunkType = RECYCLED_CHUNK;
}
gChunksBySize.Insert(node);
xprev.reset(prev);
}
gRecycledSize += aSize;
}
static void chunk_dealloc(void* aChunk, size_t aSize, ChunkType aType) {
MOZ_ASSERT(aChunk);
MOZ_ASSERT(GetChunkOffsetForPtr(aChunk) == 0);
MOZ_ASSERT(aSize != 0);
MOZ_ASSERT((aSize & kChunkSizeMask) == 0);
gChunkRTree.Unset(aChunk);
if (CAN_RECYCLE(aSize)) {
size_t recycled_so_far = gRecycledSize;
// In case some race condition put us above the limit.
if (recycled_so_far < gRecycleLimit) {
size_t recycle_remaining = gRecycleLimit - recycled_so_far;
size_t to_recycle;
if (aSize > recycle_remaining) {
to_recycle = recycle_remaining;
// Drop pages that would overflow the recycle limit
pages_trim(aChunk, aSize, 0, to_recycle);
} else {
to_recycle = aSize;
}
chunk_record(aChunk, to_recycle, aType);
return;
}
}
pages_unmap(aChunk, aSize);
}
#undef CAN_RECYCLE
// End chunk management functions.
// ***************************************************************************
// Begin arena.
static inline arena_t* thread_local_arena(bool enabled) {
arena_t* arena;
if (enabled) {
// The arena will essentially be leaked if this function is
// called with `false`, but it doesn't matter at the moment.
// because in practice nothing actually calls this function
// with `false`, except maybe at shutdown.
arena =
gArenas.CreateArena(/* aIsPrivate = */ false, /* aParams = */ nullptr);
} else {
arena = gArenas.GetDefault();
}
thread_arena.set(arena);
return arena;
}
inline void MozJemalloc::jemalloc_thread_local_arena(bool aEnabled) {
if (malloc_init()) {
thread_local_arena(aEnabled);
}
}
// Choose an arena based on a per-thread value.
static inline arena_t* choose_arena(size_t size) {
arena_t* ret = nullptr;
// We can only use TLS if this is a PIC library, since for the static
// library version, libc's malloc is used by TLS allocation, which
// introduces a bootstrapping issue.
if (size > kMaxQuantumClass) {
// Force the default arena for larger allocations.
ret = gArenas.GetDefault();
} else {
// Check TLS to see if our thread has requested a pinned arena.
ret = thread_arena.get();
// If ret is non-null, it must not be in the first page.
MOZ_DIAGNOSTIC_ASSERT_IF(ret, (size_t)ret >= gPageSize);
if (!ret) {
// Nothing in TLS. Pin this thread to the default arena.
ret = thread_local_arena(false);
}
}
MOZ_DIAGNOSTIC_ASSERT(ret);
return ret;
}
inline uint8_t arena_t::FindFreeBitInMask(uint32_t aMask, uint32_t& aRng) {
if (mPRNG != nullptr) {
if (aRng == UINT_MAX) {
aRng = mPRNG->next() % 32;
}
uint8_t bitIndex;
// RotateRight asserts when provided bad input.
aMask = aRng ? RotateRight(aMask, aRng)
: aMask; // Rotate the mask a random number of slots
bitIndex = CountTrailingZeroes32(aMask);
return (bitIndex + aRng) % 32;
}
return CountTrailingZeroes32(aMask);
}
inline void* arena_t::ArenaRunRegAlloc(arena_run_t* aRun, arena_bin_t* aBin) {
void* ret;
unsigned i, mask, bit, regind;
uint32_t rndPos = UINT_MAX;
MOZ_DIAGNOSTIC_ASSERT(aRun->mMagic == ARENA_RUN_MAGIC);
MOZ_ASSERT(aRun->mRegionsMinElement < aBin->mRunNumRegionsMask);
// Move the first check outside the loop, so that aRun->mRegionsMinElement can
// be updated unconditionally, without the possibility of updating it
// multiple times.
i = aRun->mRegionsMinElement;
mask = aRun->mRegionsMask[i];
if (mask != 0) {
bit = FindFreeBitInMask(mask, rndPos);
regind = ((i << (LOG2(sizeof(int)) + 3)) + bit);
MOZ_ASSERT(regind < aBin->mRunNumRegions);
ret = (void*)(((uintptr_t)aRun) + aBin->mRunFirstRegionOffset +
(aBin->mSizeClass * regind));
// Clear bit.
mask ^= (1U << bit);
aRun->mRegionsMask[i] = mask;
return ret;
}
for (i++; i < aBin->mRunNumRegionsMask; i++) {
mask = aRun->mRegionsMask[i];
if (mask != 0) {
bit = FindFreeBitInMask(mask, rndPos);
regind = ((i << (LOG2(sizeof(int)) + 3)) + bit);
MOZ_ASSERT(regind < aBin->mRunNumRegions);
ret = (void*)(((uintptr_t)aRun) + aBin->mRunFirstRegionOffset +
(aBin->mSizeClass * regind));
// Clear bit.
mask ^= (1U << bit);
aRun->mRegionsMask[i] = mask;
// Make a note that nothing before this element
// contains a free region.
aRun->mRegionsMinElement = i; // Low payoff: + (mask == 0);
return ret;
}
}
// Not reached.
MOZ_DIAGNOSTIC_ASSERT(0);
return nullptr;
}
static inline void arena_run_reg_dalloc(arena_run_t* run, arena_bin_t* bin,
void* ptr, size_t size) {
uint32_t diff, regind;
unsigned elm, bit;
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
// Avoid doing division with a variable divisor if possible. Using
// actual division here can reduce allocator throughput by over 20%!
diff =
(uint32_t)((uintptr_t)ptr - (uintptr_t)run - bin->mRunFirstRegionOffset);
MOZ_ASSERT(diff <=
(static_cast<unsigned>(bin->mRunSizePages) << gPageSize2Pow));
regind = diff / bin->mSizeDivisor;
MOZ_DIAGNOSTIC_ASSERT(diff == regind * size);
MOZ_DIAGNOSTIC_ASSERT(regind < bin->mRunNumRegions);
elm = regind >> (LOG2(sizeof(int)) + 3);
if (elm < run->mRegionsMinElement) {
run->mRegionsMinElement = elm;
}
bit = regind - (elm << (LOG2(sizeof(int)) + 3));
MOZ_RELEASE_ASSERT((run->mRegionsMask[elm] & (1U << bit)) == 0,
"Double-free?");
run->mRegionsMask[elm] |= (1U << bit);
}
bool arena_t::SplitRun(arena_run_t* aRun, size_t aSize, bool aLarge,
bool aZero) {
arena_chunk_t* chunk = GetChunkForPtr(aRun);
size_t old_ndirty = chunk->ndirty;
size_t run_ind =
(unsigned)((uintptr_t(aRun) - uintptr_t(chunk)) >> gPageSize2Pow);
size_t total_pages =
(chunk->map[run_ind].bits & ~gPageSizeMask) >> gPageSize2Pow;
size_t need_pages = (aSize >> gPageSize2Pow);
MOZ_ASSERT(need_pages > 0);
MOZ_ASSERT(need_pages <= total_pages);
size_t rem_pages = total_pages - need_pages;
MOZ_ASSERT((chunk->map[run_ind].bits & CHUNK_MAP_BUSY) == 0);
#ifdef MALLOC_DECOMMIT
size_t i = 0;
while (i < need_pages) {
MOZ_ASSERT((chunk->map[run_ind + i].bits & CHUNK_MAP_BUSY) == 0);
// Commit decommitted pages if necessary. If a decommitted
// page is encountered, commit all needed adjacent decommitted
// pages in one operation, in order to reduce system call
// overhead.
if (chunk->map[run_ind + i].bits & CHUNK_MAP_DECOMMITTED) {
// Advance i+j to just past the index of the last page
// to commit. Clear CHUNK_MAP_DECOMMITTED along the way.
size_t j;
for (j = 0; i + j < need_pages &&
(chunk->map[run_ind + i + j].bits & CHUNK_MAP_DECOMMITTED);
j++) {
// DECOMMITTED, MADVISED and FRESH are mutually exclusive.
MOZ_ASSERT((chunk->map[run_ind + i + j].bits &
(CHUNK_MAP_FRESH | CHUNK_MAP_MADVISED)) == 0);
}
// Consider committing more pages to amortise calls to VirtualAlloc.
// This only makes sense at the edge of our run hence the if condition
// here.
if (i + j == need_pages) {
size_t extra_commit = ExtraCommitPages(j, rem_pages);
for (; i + j < need_pages + extra_commit &&
(chunk->map[run_ind + i + j].bits &
CHUNK_MAP_MADVISED_OR_DECOMMITTED);
j++) {
MOZ_ASSERT((chunk->map[run_ind + i + j].bits &
(CHUNK_MAP_FRESH | CHUNK_MAP_MADVISED)) == 0);
}
}
if (!pages_commit(
(void*)(uintptr_t(chunk) + ((run_ind + i) << gPageSize2Pow)),
j << gPageSize2Pow)) {
return false;
}
// pages_commit zeroes pages, so mark them as such if it succeeded.
// That's checked further below to avoid manually zeroing the pages.
for (size_t k = 0; k < j; k++) {
chunk->map[run_ind + i + k].bits =
(chunk->map[run_ind + i + k].bits & ~CHUNK_MAP_DECOMMITTED) |
CHUNK_MAP_ZEROED | CHUNK_MAP_FRESH;
}
mNumFresh += j;
i += j;
} else {
i++;
}
}
#endif
mRunsAvail.Remove(&chunk->map[run_ind]);
// Keep track of trailing unused pages for later use.
if (rem_pages > 0) {
chunk->map[run_ind + need_pages].bits =
(rem_pages << gPageSize2Pow) |
(chunk->map[run_ind + need_pages].bits & gPageSizeMask);
chunk->map[run_ind + total_pages - 1].bits =
(rem_pages << gPageSize2Pow) |
(chunk->map[run_ind + total_pages - 1].bits & gPageSizeMask);
mRunsAvail.Insert(&chunk->map[run_ind + need_pages]);
}
for (size_t i = 0; i < need_pages; i++) {
// Zero if necessary.
if (aZero) {
if ((chunk->map[run_ind + i].bits & CHUNK_MAP_ZEROED) == 0) {
memset((void*)(uintptr_t(chunk) + ((run_ind + i) << gPageSize2Pow)), 0,
gPageSize);
// CHUNK_MAP_ZEROED is cleared below.
}
}
// Update dirty page accounting.
if (chunk->map[run_ind + i].bits & CHUNK_MAP_DIRTY) {
chunk->ndirty--;
mNumDirty--;
// CHUNK_MAP_DIRTY is cleared below.
} else if (chunk->map[run_ind + i].bits & CHUNK_MAP_MADVISED) {
mStats.committed++;
mNumMAdvised--;
}
if (chunk->map[run_ind + i].bits & CHUNK_MAP_FRESH) {
mStats.committed++;
mNumFresh--;
}
// This bit has already been cleared
MOZ_ASSERT(!(chunk->map[run_ind + i].bits & CHUNK_MAP_DECOMMITTED));
// Initialize the chunk map. This clears the dirty, zeroed and madvised
// bits, decommitted is cleared above.
if (aLarge) {
chunk->map[run_ind + i].bits = CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
} else {
chunk->map[run_ind + i].bits = size_t(aRun) | CHUNK_MAP_ALLOCATED;
}
}
// Set the run size only in the first element for large runs. This is
// primarily a debugging aid, since the lack of size info for trailing
// pages only matters if the application tries to operate on an
// interior pointer.
if (aLarge) {
chunk->map[run_ind].bits |= aSize;
}
if (chunk->ndirty == 0 && old_ndirty > 0 && !chunk->mIsPurging) {
mChunksDirty.Remove(chunk);
}
return true;
}
void arena_t::InitChunk(arena_chunk_t* aChunk, size_t aMinCommittedPages) {
mStats.mapped += kChunkSize;
aChunk->arena = this;
// Claim that no pages are in use, since the header is merely overhead.
aChunk->ndirty = 0;
aChunk->mIsPurging = false;
aChunk->mDying = false;
// Setup the chunk's pages in two phases. First we mark which pages are
// committed & decommitted and perform the decommit. Then we update the map
// to create the runs.
// Clear the bits for the real header pages.
size_t i;
for (i = 0; i < gChunkHeaderNumPages - 1; i++) {
aChunk->map[i].bits = 0;
}
mStats.committed += gChunkHeaderNumPages - 1;
// Decommit the last header page (=leading page) as a guard.
pages_decommit((void*)(uintptr_t(aChunk) + (i << gPageSize2Pow)), gPageSize);
aChunk->map[i++].bits = CHUNK_MAP_DECOMMITTED;
// If MALLOC_DECOMMIT is enabled then commit only the pages we're about to
// use. Otherwise commit all of them.
#ifdef MALLOC_DECOMMIT
size_t n_fresh_pages =
aMinCommittedPages +
ExtraCommitPages(
aMinCommittedPages,
gChunkNumPages - gChunkHeaderNumPages - aMinCommittedPages - 1);
#else
size_t n_fresh_pages = gChunkNumPages - 1 - gChunkHeaderNumPages;
#endif
// The committed pages are marked as Fresh. Our caller, SplitRun will update
// this when it uses them.
for (size_t j = 0; j < n_fresh_pages; j++) {
aChunk->map[i + j].bits = CHUNK_MAP_ZEROED | CHUNK_MAP_FRESH;
}
i += n_fresh_pages;
mNumFresh += n_fresh_pages;
#ifndef MALLOC_DECOMMIT
// If MALLOC_DECOMMIT isn't defined then all the pages are fresh and setup in
// the loop above.
MOZ_ASSERT(i == gChunkNumPages - 1);
#endif
// If MALLOC_DECOMMIT is defined, then this will decommit the remainder of the
// chunk plus the last page which is a guard page, if it is not defined it
// will only decommit the guard page.
pages_decommit((void*)(uintptr_t(aChunk) + (i << gPageSize2Pow)),
(gChunkNumPages - i) << gPageSize2Pow);
for (; i < gChunkNumPages; i++) {
aChunk->map[i].bits = CHUNK_MAP_DECOMMITTED;
}
// aMinCommittedPages will create a valid run.
MOZ_ASSERT(aMinCommittedPages > 0);
MOZ_ASSERT(aMinCommittedPages <= gChunkNumPages - gChunkHeaderNumPages - 1);
// Create the run.
aChunk->map[gChunkHeaderNumPages].bits |= gMaxLargeClass;
aChunk->map[gChunkNumPages - 2].bits |= gMaxLargeClass;
mRunsAvail.Insert(&aChunk->map[gChunkHeaderNumPages]);
#ifdef MALLOC_DOUBLE_PURGE
new (&aChunk->chunks_madvised_elem) DoublyLinkedListElement<arena_chunk_t>();
#endif
}
bool arena_t::RemoveChunk(arena_chunk_t* aChunk) {
aChunk->mDying = true;
// If the chunk has busy pages that means that a Purge() is in progress.
// We can't remove the chunk now, instead Purge() will do it.
if (aChunk->mIsPurging) {
return false;
}
if (aChunk->ndirty > 0) {
MOZ_ASSERT(aChunk->arena == this);
mChunksDirty.Remove(aChunk);
mNumDirty -= aChunk->ndirty;
mStats.committed -= aChunk->ndirty;
}
// Count the number of madvised/fresh pages and update the stats.
size_t madvised = 0;
size_t fresh = 0;
for (size_t i = gChunkHeaderNumPages; i < gChunkNumPages - 1; i++) {
// There must not be any pages that are not fresh, madvised, decommitted
// or dirty.
MOZ_ASSERT(aChunk->map[i].bits &
(CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED | CHUNK_MAP_DIRTY));
MOZ_ASSERT((aChunk->map[i].bits & CHUNK_MAP_BUSY) == 0);
if (aChunk->map[i].bits & CHUNK_MAP_MADVISED) {
madvised++;
} else if (aChunk->map[i].bits & CHUNK_MAP_FRESH) {
fresh++;
}
}
mNumMAdvised -= madvised;
mNumFresh -= fresh;
#ifdef MALLOC_DOUBLE_PURGE
if (mChunksMAdvised.ElementProbablyInList(aChunk)) {
mChunksMAdvised.remove(aChunk);
}
#endif
mStats.mapped -= kChunkSize;
mStats.committed -= gChunkHeaderNumPages - 1;
return true;
}
bool arena_chunk_t::IsEmpty() {
return (map[gChunkHeaderNumPages].bits &
(~gPageSizeMask | CHUNK_MAP_ALLOCATED)) == gMaxLargeClass;
}
arena_chunk_t* arena_t::DemoteChunkToSpare(arena_chunk_t* aChunk) {
if (mSpare) {
if (!RemoveChunk(mSpare)) {
// If we can't remove the spare chunk now purge will finish removing it
// later. Set it to null so that the return below will return null and
// our caller won't delete the chunk before Purge() is finished.
mSpare = nullptr;
}
}
arena_chunk_t* chunk_dealloc = mSpare;
mSpare = aChunk;
return chunk_dealloc;
}
arena_run_t* arena_t::AllocRun(size_t aSize, bool aLarge, bool aZero) {
arena_run_t* run;
arena_chunk_map_t* mapelm;
arena_chunk_map_t key;
MOZ_ASSERT(aSize <= gMaxLargeClass);
MOZ_ASSERT((aSize & gPageSizeMask) == 0);
// Search the arena's chunks for the lowest best fit.
key.bits = aSize | CHUNK_MAP_KEY;
mapelm = mRunsAvail.SearchOrNext(&key);
if (mapelm) {
arena_chunk_t* chunk = GetChunkForPtr(mapelm);
size_t pageind =
(uintptr_t(mapelm) - uintptr_t(chunk->map)) / sizeof(arena_chunk_map_t);
MOZ_ASSERT((chunk->map[pageind].bits & CHUNK_MAP_BUSY) == 0);
run = (arena_run_t*)(uintptr_t(chunk) + (pageind << gPageSize2Pow));
} else if (mSpare && !mSpare->mIsPurging) {
// Use the spare.
arena_chunk_t* chunk = mSpare;
mSpare = nullptr;
run = (arena_run_t*)(uintptr_t(chunk) +
(gChunkHeaderNumPages << gPageSize2Pow));
// Insert the run into the tree of available runs.
MOZ_ASSERT((chunk->map[gChunkHeaderNumPages].bits & CHUNK_MAP_BUSY) == 0);
mRunsAvail.Insert(&chunk->map[gChunkHeaderNumPages]);
} else {
// No usable runs. Create a new chunk from which to allocate
// the run.
arena_chunk_t* chunk =
(arena_chunk_t*)chunk_alloc(kChunkSize, kChunkSize, false);
if (!chunk) {
return nullptr;
}
InitChunk(chunk, aSize >> gPageSize2Pow);
run = (arena_run_t*)(uintptr_t(chunk) +
(gChunkHeaderNumPages << gPageSize2Pow));
}
// Update page map.
return SplitRun(run, aSize, aLarge, aZero) ? run : nullptr;
}
void arena_t::UpdateMaxDirty() {
MaybeMutexAutoLock lock(mLock);
int32_t modifier = gArenas.DefaultMaxDirtyPageModifier();
if (modifier) {
int32_t arenaOverride =
modifier > 0 ? mMaxDirtyIncreaseOverride : mMaxDirtyDecreaseOverride;
if (arenaOverride) {
modifier = arenaOverride;
}
}
mMaxDirty =
modifier >= 0 ? mMaxDirtyBase << modifier : mMaxDirtyBase >> -modifier;
}
#ifdef MALLOC_DECOMMIT
size_t arena_t::ExtraCommitPages(size_t aReqPages, size_t aRemainingPages) {
const int32_t modifier = gArenas.DefaultMaxDirtyPageModifier();
if (modifier < 0) {
return 0;
}
// The maximum size of the page cache
const size_t max_page_cache = mMaxDirty;
// The current size of the page cache, note that we use mNumFresh +
// mNumMAdvised here but Purge() does not.
const size_t page_cache = mNumDirty + mNumFresh + mNumMAdvised;
if (page_cache > max_page_cache) {
// We're already exceeding our dirty page count even though we're trying
// to allocate. This can happen due to fragmentation. Don't commit
// excess memory since we're probably here due to a larger allocation and
// small amounts of memory are certainly available in the page cache.
return 0;
}
if (modifier > 0) {
// If modifier is > 0 then we want to keep all the pages we can, but don't
// exceed the size of the page cache. The subtraction cannot underflow
// because of the condition above.
return std::min(aRemainingPages, max_page_cache - page_cache);
}
// The rest is arbitrary and involves a some assumptions. I've broken it down
// into simple expressions to document them more clearly.
// Assumption 1: a quarter of mMaxDirty is a sensible "minimum
// target" for the dirty page cache. Likewise 3 quarters is a sensible
// "maximum target". Note that for the maximum we avoid using the whole page
// cache now so that a free that follows this allocation doesn't immeidatly
// call Purge (churning memory).
const size_t min = max_page_cache / 4;
const size_t max = 3 * max_page_cache / 4;
// Assumption 2: Committing 32 pages at a time is sufficient to amortise
// VirtualAlloc costs.
size_t amortisation_threshold = 32;
// extra_pages is the number of additional pages needed to meet
// amortisation_threshold.
size_t extra_pages = aReqPages < amortisation_threshold
? amortisation_threshold - aReqPages
: 0;
// If committing extra_pages isn't enough to hit the minimum target then
// increase it.
if (page_cache + extra_pages < min) {
extra_pages = min - page_cache;
} else if (page_cache + extra_pages > max) {
// If committing extra_pages would exceed our maximum target then it may
// still be useful to allocate extra pages. One of the reasons this can
// happen could be fragmentation of the cache,
// Therefore reduce the amortisation threshold so that we might allocate
// some extra pages but avoid exceeding the dirty page cache.
amortisation_threshold /= 2;
extra_pages = std::min(aReqPages < amortisation_threshold
? amortisation_threshold - aReqPages
: 0,
max_page_cache - page_cache);
}
// Cap extra_pages to aRemainingPages and adjust aRemainingPages. We will
// commit at least this many extra pages.
extra_pages = std::min(extra_pages, aRemainingPages);
// Finally if commiting a small number of additional pages now can prevent
// a small commit later then try to commit a little more now, provided we
// don't exceed max_page_cache.
if ((aRemainingPages - extra_pages) < amortisation_threshold / 2 &&
(page_cache + aRemainingPages) < max_page_cache) {
return aRemainingPages;
}
return extra_pages;
}
#endif
arena_t::PurgeResult arena_t::Purge(PurgeCondition aCond) {
arena_chunk_t* chunk;
// The first critical section will find a chunk and mark dirty pages in it as
// busy.
{
MaybeMutexAutoLock lock(mLock);
if (mMustDeleteAfterPurge) {
mIsPurgePending = false;
return Dying;
}
#ifdef MOZ_DEBUG
size_t ndirty = 0;
for (auto* chunk : mChunksDirty.iter()) {
ndirty += chunk->ndirty;
}
// Not all dirty chunks are in mChunksDirty as others might be being Purged.
MOZ_ASSERT(ndirty <= mNumDirty);
#endif
if (!ShouldContinuePurge(aCond)) {
mIsPurgePending = false;
return Done;
}
// Take a single chunk and attempt to purge some of its dirty pages. The
// loop below will purge memory from the chunk until either:
// * The dirty page count for the arena hits its target,
// * Another thread attempts to delete this chunk, or
// * The chunk has no more dirty pages.
// In any of these cases the loop will break and Purge() will return, which
// means it may return before the arena meets its dirty page count target,
// the return value is used by the caller to call Purge() again where it
// will take the next chunk with dirty pages.
chunk = mChunksDirty.Last();
if (!chunk) {
// There are chunks with dirty pages (because mNumDirty > 0 above) but
// they're not in mChunksDirty. That can happen if they're busy being
// purged by other threads.
// We have to clear the flag to preserve the invariant that if Purge()
// returns false the flag is clear, if there's more purging work to do in
// other chunks then either other calls to Purge() (in other threads) will
// handle it or we rely on ShouldStartPurge() returning true at some point
// in the future.
mIsPurgePending = false;
return Busy;
}
MOZ_ASSERT(chunk->ndirty > 0);
// Mark the chunk as busy so it won't be deleted and remove it from
// mChunksDirty so we're the only thread purging it.
MOZ_ASSERT(!chunk->mIsPurging);
mChunksDirty.Remove(chunk);
chunk->mIsPurging = true;
} // MaybeMutexAutoLock
// True if we should continue purging memory from this arena.
bool continue_purge_arena = true;
// True if we should continue purging memory in this chunk.
bool continue_purge_chunk = true;
// True if at least one Purge operation has occured and therefore we need to
// call FinishPurgingInChunk() before returning.
bool purged_once = false;
while (continue_purge_chunk && continue_purge_arena) {
// This structure is used to communicate between the two PurgePhase
// functions.
PurgeInfo purge_info(*this, chunk);
{
// Phase 1: Find pages that need purging.
MaybeMutexAutoLock lock(purge_info.mArena.mLock);
MOZ_ASSERT(chunk->mIsPurging);
if (purge_info.mArena.mMustDeleteAfterPurge) {
chunk->mIsPurging = false;
purge_info.mArena.mIsPurgePending = false;
return Dying;
}
continue_purge_chunk = purge_info.FindDirtyPages(purged_once);
continue_purge_arena = purge_info.mArena.ShouldContinuePurge(aCond);
// The code below will exit returning false if these are both false, so
// clear mIsDeferredPurgeNeeded while we still hold the lock.
if (!continue_purge_chunk && !continue_purge_arena) {
purge_info.mArena.mIsPurgePending = false;
}
}
if (!continue_purge_chunk) {
if (chunk->mDying) {
// Phase one already unlinked the chunk from structures, we just need to
// release the memory.
chunk_dealloc((void*)chunk, kChunkSize, ARENA_CHUNK);
}
// There's nothing else to do here, our caller may execute Purge() again
// if continue_purge_arena is true.
return continue_purge_arena ? Continue : Done;
}
#ifdef MALLOC_DECOMMIT
pages_decommit(purge_info.DirtyPtr(), purge_info.DirtyLenBytes());
#else
# ifdef XP_SOLARIS
posix_madvise(purge_info.DirtyPtr(), purge_info.DirtyLenBytes(), MADV_FREE);
# else
madvise(purge_info.DirtyPtr(), purge_info.DirtyLenBytes(), MADV_FREE);
# endif
#endif
arena_chunk_t* chunk_to_release = nullptr;
bool is_dying;
{
// Phase 2: Mark the pages with their final state (madvised or
// decommitted) and fix up any other bookkeeping.
MaybeMutexAutoLock lock(purge_info.mArena.mLock);
MOZ_ASSERT(chunk->mIsPurging);
// We can't early exit if the arena is dying, we have to finish the purge
// (which restores the state so the destructor will check it) and maybe
// release the old spare arena.
is_dying = purge_info.mArena.mMustDeleteAfterPurge;
auto [cpc, ctr] = purge_info.UpdatePagesAndCounts();
continue_purge_chunk = cpc;
chunk_to_release = ctr;
continue_purge_arena = purge_info.mArena.ShouldContinuePurge(aCond);
if (!continue_purge_chunk || !continue_purge_arena) {
// We're going to stop purging here so update the chunk's bookkeeping.
purge_info.FinishPurgingInChunk(true);
purge_info.mArena.mIsPurgePending = false;
}
} // MaybeMutexAutoLock
// Phase 2 can release the spare chunk (not always == chunk) so an extra
// parameter is used to return that chunk.
if (chunk_to_release) {
chunk_dealloc((void*)chunk_to_release, kChunkSize, ARENA_CHUNK);
}
if (is_dying) {
return Dying;
}
purged_once = true;
}
return continue_purge_arena ? Continue : Done;
}
bool arena_t::PurgeInfo::FindDirtyPages(bool aPurgedOnce) {
// It's possible that the previously dirty pages have now been
// allocated or the chunk is dying.
if (mChunk->ndirty == 0 || mChunk->mDying) {
// Add the chunk to the mChunksMAdvised list if it's had at least one
// madvise.
FinishPurgingInChunk(aPurgedOnce);
return false;
}
// Look for the first dirty page, as we do record the beginning of the run
// that contains the dirty page.
bool previous_page_is_allocated = true;
for (size_t i = gChunkHeaderNumPages; i < gChunkNumPages - 1; i++) {
size_t bits = mChunk->map[i].bits;
// We must not find any busy pages because this chunk shouldn't be in
// the dirty list.
MOZ_ASSERT((bits & CHUNK_MAP_BUSY) == 0);
// The first page belonging to a free run has the allocated bit clear
// and a non-zero size. To distinguish it from the last page of a free
// run we track the allocated bit of the previous page, if it's set
// then this is the first.
if ((bits & CHUNK_MAP_ALLOCATED) == 0 && (bits & ~gPageSizeMask) != 0 &&
previous_page_is_allocated) {
mFreeRunInd = i;
mFreeRunLen = bits >> gPageSize2Pow;
}
if (bits & CHUNK_MAP_DIRTY) {
MOZ_ASSERT(
(mChunk->map[i].bits & CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED) == 0);
mDirtyInd = i;
break;
}
previous_page_is_allocated = bits & CHUNK_MAP_ALLOCATED;
}
MOZ_ASSERT(mDirtyInd != 0);
MOZ_ASSERT(mFreeRunInd >= gChunkHeaderNumPages);
MOZ_ASSERT(mFreeRunInd <= mDirtyInd);
MOZ_ASSERT(mFreeRunLen > 0);
// Look for the next not-dirty page, it could be the guard page at the end
// of the chunk.
for (size_t i = 0; mDirtyInd + i < gChunkNumPages; i++) {
size_t& bits = mChunk->map[mDirtyInd + i].bits;
// We must not find any busy pages because this chunk shouldn't be in the
// dirty list.
MOZ_ASSERT(!(bits & CHUNK_MAP_BUSY));
if (!(bits & CHUNK_MAP_DIRTY)) {
mDirtyNPages = i;
break;
}
MOZ_ASSERT((bits & CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED) == 0);
bits ^= CHUNK_MAP_DIRTY;
}
MOZ_ASSERT(mDirtyNPages > 0);
MOZ_ASSERT(mDirtyNPages <= mChunk->ndirty);
MOZ_ASSERT(mFreeRunInd + mFreeRunLen >= mDirtyInd + mDirtyNPages);
// Mark the run as busy so that another thread freeing memory won't try to
// coalesce it.
mChunk->map[mFreeRunInd].bits |= CHUNK_MAP_BUSY;
mChunk->map[FreeRunLastInd()].bits |= CHUNK_MAP_BUSY;
mChunk->ndirty -= mDirtyNPages;
mArena.mNumDirty -= mDirtyNPages;
// Before we unlock ensure that no other thread can allocate from these
// pages.
if (mArena.mSpare != mChunk) {
mArena.mRunsAvail.Remove(&mChunk->map[mFreeRunInd]);
}
return true;
}
std::pair<bool, arena_chunk_t*> arena_t::PurgeInfo::UpdatePagesAndCounts() {
for (size_t i = 0; i < mDirtyNPages; i++) {
// The page must not have any of the madvised, decommited or dirty bits
// set.
MOZ_ASSERT((mChunk->map[mDirtyInd + i].bits &
(CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED | CHUNK_MAP_DIRTY)) ==
0);
#ifdef MALLOC_DECOMMIT
const size_t free_operation = CHUNK_MAP_DECOMMITTED;
#else
const size_t free_operation = CHUNK_MAP_MADVISED;
#endif
mChunk->map[mDirtyInd + i].bits ^= free_operation;
}
// Remove the CHUNK_MAP_BUSY marks from the run.
#ifdef MOZ_DEBUG
MOZ_ASSERT(mChunk->map[mFreeRunInd].bits & CHUNK_MAP_BUSY);
MOZ_ASSERT(mChunk->map[FreeRunLastInd()].bits & CHUNK_MAP_BUSY);
#endif
mChunk->map[mFreeRunInd].bits &= ~CHUNK_MAP_BUSY;
mChunk->map[FreeRunLastInd()].bits &= ~CHUNK_MAP_BUSY;
#ifndef MALLOC_DECOMMIT
mArena.mNumMAdvised += mDirtyNPages;
#endif
mArena.mStats.committed -= mDirtyNPages;
if (mChunk->mDying) {
// A dying chunk doesn't need to be coaleased, it will already have one
// large run.
MOZ_ASSERT(mFreeRunInd == gChunkHeaderNumPages &&
mFreeRunLen == gChunkNumPages - gChunkHeaderNumPages - 1);
return std::make_pair(false, mChunk);
}
bool was_empty = mChunk->IsEmpty();
mFreeRunInd =
mArena.TryCoalesce(mChunk, mFreeRunInd, mFreeRunLen, FreeRunLenBytes());
arena_chunk_t* chunk_to_release = nullptr;
if (!was_empty && mChunk->IsEmpty()) {
// This now-empty chunk will become the spare chunk and the spare
// chunk will be returned for deletion.
chunk_to_release = mArena.DemoteChunkToSpare(mChunk);
}
if (mChunk != mArena.mSpare) {
mArena.mRunsAvail.Insert(&mChunk->map[mFreeRunInd]);
}
return std::make_pair(mChunk->ndirty != 0, chunk_to_release);
}
void arena_t::PurgeInfo::FinishPurgingInChunk(bool aAddToMAdvised) {
// If there's no more purge activity for this chunk then finish up while
// we still have the lock.
MOZ_ASSERT(mChunk->mIsPurging);
mChunk->mIsPurging = false;
if (mChunk->mDying) {
// Another thread tried to delete this chunk while we weren't holding
// the lock. Now it's our responsibility to finish deleting it. First
// clear its dirty pages so that RemoveChunk() doesn't try to remove it
// from mChunksDirty because it won't be there.
mArena.mNumDirty -= mChunk->ndirty;
mArena.mStats.committed -= mChunk->ndirty;
mChunk->ndirty = 0;
DebugOnly<bool> release_chunk = mArena.RemoveChunk(mChunk);
// RemoveChunk() can't return false because mIsPurging was false
// during the call.
MOZ_ASSERT(release_chunk);
return;
}
if (mChunk->ndirty != 0) {
mArena.mChunksDirty.Insert(mChunk);
}
#ifdef MALLOC_DOUBLE_PURGE
if (aAddToMAdvised) {
// The chunk might already be in the list, but this
// makes sure it's at the front.
if (mArena.mChunksMAdvised.ElementProbablyInList(mChunk)) {
mArena.mChunksMAdvised.remove(mChunk);
}
mArena.mChunksMAdvised.pushFront(mChunk);
}
#endif
}
// run_pages and size make each-other redundant. But we use them both and the
// caller computes both so this function requires both and will assert if they
// are inconsistent.
size_t arena_t::TryCoalesce(arena_chunk_t* aChunk, size_t run_ind,
size_t run_pages, size_t size) {
// Copy in/out parameters to local variables so that we don't need '*'
// operators throughout this code but also so that type checking is stricter
// (references are too easily coerced).
MOZ_ASSERT(size == run_pages << gPageSize2Pow);
// Try to coalesce forward.
if (run_ind + run_pages < gChunkNumPages - 1 &&
(aChunk->map[run_ind + run_pages].bits &
(CHUNK_MAP_ALLOCATED | CHUNK_MAP_BUSY)) == 0) {
size_t nrun_size = aChunk->map[run_ind + run_pages].bits & ~gPageSizeMask;
// Remove successor from tree of available runs; the coalesced run is
// inserted later.
mRunsAvail.Remove(&aChunk->map[run_ind + run_pages]);
size += nrun_size;
run_pages = size >> gPageSize2Pow;
MOZ_DIAGNOSTIC_ASSERT((aChunk->map[run_ind + run_pages - 1].bits &
~gPageSizeMask) == nrun_size);
aChunk->map[run_ind].bits =
size | (aChunk->map[run_ind].bits & gPageSizeMask);
aChunk->map[run_ind + run_pages - 1].bits =
size | (aChunk->map[run_ind + run_pages - 1].bits & gPageSizeMask);
}
// Try to coalesce backward.
if (run_ind > gChunkHeaderNumPages &&
(aChunk->map[run_ind - 1].bits &
(CHUNK_MAP_ALLOCATED | CHUNK_MAP_BUSY)) == 0) {
size_t prun_size = aChunk->map[run_ind - 1].bits & ~gPageSizeMask;
run_ind -= prun_size >> gPageSize2Pow;
// Remove predecessor from tree of available runs; the coalesced run is
// inserted later.
mRunsAvail.Remove(&aChunk->map[run_ind]);
size += prun_size;
run_pages = size >> gPageSize2Pow;
MOZ_DIAGNOSTIC_ASSERT((aChunk->map[run_ind].bits & ~gPageSizeMask) ==
prun_size);
aChunk->map[run_ind].bits =
size | (aChunk->map[run_ind].bits & gPageSizeMask);
aChunk->map[run_ind + run_pages - 1].bits =
size | (aChunk->map[run_ind + run_pages - 1].bits & gPageSizeMask);
}
return run_ind;
}
arena_chunk_t* arena_t::DallocRun(arena_run_t* aRun, bool aDirty) {
arena_chunk_t* chunk;
size_t size, run_ind, run_pages;
chunk = GetChunkForPtr(aRun);
run_ind = (size_t)((uintptr_t(aRun) - uintptr_t(chunk)) >> gPageSize2Pow);
MOZ_DIAGNOSTIC_ASSERT(run_ind >= gChunkHeaderNumPages);
MOZ_RELEASE_ASSERT(run_ind < gChunkNumPages - 1);
if ((chunk->map[run_ind].bits & CHUNK_MAP_LARGE) != 0) {
size = chunk->map[run_ind].bits & ~gPageSizeMask;
run_pages = (size >> gPageSize2Pow);
} else {
run_pages = aRun->mBin->mRunSizePages;
size = run_pages << gPageSize2Pow;
}
// Mark pages as unallocated in the chunk map.
if (aDirty) {
size_t i;
for (i = 0; i < run_pages; i++) {
MOZ_DIAGNOSTIC_ASSERT((chunk->map[run_ind + i].bits & CHUNK_MAP_DIRTY) ==
0);
chunk->map[run_ind + i].bits = CHUNK_MAP_DIRTY;
}
if (chunk->ndirty == 0 && !chunk->mIsPurging) {
mChunksDirty.Insert(chunk);
}
chunk->ndirty += run_pages;
mNumDirty += run_pages;
} else {
size_t i;
for (i = 0; i < run_pages; i++) {
chunk->map[run_ind + i].bits &= ~(CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED);
}
}
chunk->map[run_ind].bits = size | (chunk->map[run_ind].bits & gPageSizeMask);
chunk->map[run_ind + run_pages - 1].bits =
size | (chunk->map[run_ind + run_pages - 1].bits & gPageSizeMask);
run_ind = TryCoalesce(chunk, run_ind, run_pages, size);
// Deallocate chunk if it is now completely unused.
arena_chunk_t* chunk_dealloc = nullptr;
if (chunk->IsEmpty()) {
chunk_dealloc = DemoteChunkToSpare(chunk);
} else {
// Insert into tree of available runs, now that coalescing is complete.
mRunsAvail.Insert(&chunk->map[run_ind]);
}
return chunk_dealloc;
}
void arena_t::TrimRunHead(arena_chunk_t* aChunk, arena_run_t* aRun,
size_t aOldSize, size_t aNewSize) {
size_t pageind = (uintptr_t(aRun) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t head_npages = (aOldSize - aNewSize) >> gPageSize2Pow;
MOZ_ASSERT(aOldSize > aNewSize);
// Update the chunk map so that arena_t::RunDalloc() can treat the
// leading run as separately allocated.
aChunk->map[pageind].bits =
(aOldSize - aNewSize) | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
aChunk->map[pageind + head_npages].bits =
aNewSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
DebugOnly<arena_chunk_t*> no_chunk = DallocRun(aRun, false);
// This will never release a chunk as there's still at least one allocated
// run.
MOZ_ASSERT(!no_chunk);
}
void arena_t::TrimRunTail(arena_chunk_t* aChunk, arena_run_t* aRun,
size_t aOldSize, size_t aNewSize, bool aDirty) {
size_t pageind = (uintptr_t(aRun) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t npages = aNewSize >> gPageSize2Pow;
MOZ_ASSERT(aOldSize > aNewSize);
// Update the chunk map so that arena_t::RunDalloc() can treat the
// trailing run as separately allocated.
aChunk->map[pageind].bits = aNewSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
aChunk->map[pageind + npages].bits =
(aOldSize - aNewSize) | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
DebugOnly<arena_chunk_t*> no_chunk =
DallocRun((arena_run_t*)(uintptr_t(aRun) + aNewSize), aDirty);
// This will never release a chunk as there's still at least one allocated
// run.
MOZ_ASSERT(!no_chunk);
}
arena_run_t* arena_t::GetNewEmptyBinRun(arena_bin_t* aBin) {
arena_run_t* run;
unsigned i, remainder;
// Allocate a new run.
run = AllocRun(static_cast<size_t>(aBin->mRunSizePages) << gPageSize2Pow,
false, false);
if (!run) {
return nullptr;
}
// Initialize run internals.
run->mBin = aBin;
for (i = 0; i < aBin->mRunNumRegionsMask - 1; i++) {
run->mRegionsMask[i] = UINT_MAX;
}
remainder = aBin->mRunNumRegions & ((1U << (LOG2(sizeof(int)) + 3)) - 1);
if (remainder == 0) {
run->mRegionsMask[i] = UINT_MAX;
} else {
// The last element has spare bits that need to be unset.
run->mRegionsMask[i] =
(UINT_MAX >> ((1U << (LOG2(sizeof(int)) + 3)) - remainder));
}
run->mRegionsMinElement = 0;
run->mNumFree = aBin->mRunNumRegions;
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
run->mMagic = ARENA_RUN_MAGIC;
#endif
// Make sure we continue to use this run for subsequent allocations.
new (&run->mRunListElem) DoublyLinkedListElement<arena_run_t>();
aBin->mNonFullRuns.pushFront(run);
aBin->mNumRuns++;
return run;
}
arena_run_t* arena_t::GetNonFullBinRun(arena_bin_t* aBin) {
auto mrf_head = aBin->mNonFullRuns.begin();
if (mrf_head) {
// Take the head and if we are going to fill it, remove it from our list.
arena_run_t* run = &(*mrf_head);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
if (run->mNumFree == 1) {
aBin->mNonFullRuns.remove(run);
}
return run;
}
return GetNewEmptyBinRun(aBin);
}
void arena_bin_t::Init(SizeClass aSizeClass) {
size_t try_run_size;
unsigned try_nregs, try_mask_nelms, try_reg0_offset;
// Size of the run header, excluding mRegionsMask.
static const size_t kFixedHeaderSize = offsetof(arena_run_t, mRegionsMask);
MOZ_ASSERT(aSizeClass.Size() <= gMaxBinClass);
try_run_size = gPageSize;
mSizeClass = aSizeClass.Size();
mNumRuns = 0;
// Run size expansion loop.
while (true) {
try_nregs = ((try_run_size - kFixedHeaderSize) / mSizeClass) +
1; // Counter-act try_nregs-- in loop.
// The do..while loop iteratively reduces the number of regions until
// the run header and the regions no longer overlap. A closed formula
// would be quite messy, since there is an interdependency between the
// header's mask length and the number of regions.
do {
try_nregs--;
try_mask_nelms =
(try_nregs >> (LOG2(sizeof(int)) + 3)) +
((try_nregs & ((1U << (LOG2(sizeof(int)) + 3)) - 1)) ? 1 : 0);
try_reg0_offset = try_run_size - (try_nregs * mSizeClass);
} while (kFixedHeaderSize + (sizeof(unsigned) * try_mask_nelms) >
try_reg0_offset);
// Try to keep the run overhead below kRunOverhead.
if (Fraction(try_reg0_offset, try_run_size) <= kRunOverhead) {
break;
}
// If the overhead is larger than the size class, it means the size class
// is small and doesn't align very well with the header. It's desirable to
// have smaller run sizes for them, so relax the overhead requirement.
if (try_reg0_offset > mSizeClass) {
if (Fraction(try_reg0_offset, try_run_size) <= kRunRelaxedOverhead) {
break;
}
}
// The run header includes one bit per region of the given size. For sizes
// small enough, the number of regions is large enough that growing the run
// size barely moves the needle for the overhead because of all those bits.
// For example, for a size of 8 bytes, adding 4KiB to the run size adds
// close to 512 bits to the header, which is 64 bytes.
// With such overhead, there is no way to get to the wanted overhead above,
// so we give up if the required size for mRegionsMask more than doubles the
// size of the run header.
if (try_mask_nelms * sizeof(unsigned) >= kFixedHeaderSize) {
break;
}
// If next iteration is going to be larger than the largest possible large
// size class, then we didn't find a setup where the overhead is small
// enough, and we can't do better than the current settings, so just use
// that.
if (try_run_size + gPageSize > gMaxLargeClass) {
break;
}
// Try more aggressive settings.
try_run_size += gPageSize;
}
MOZ_ASSERT(kFixedHeaderSize + (sizeof(unsigned) * try_mask_nelms) <=
try_reg0_offset);
MOZ_ASSERT((try_mask_nelms << (LOG2(sizeof(int)) + 3)) >= try_nregs);
// Our list management would break if mRunNumRegions == 1 and we should use
// a large size class instead, anyways.
MOZ_ASSERT(try_nregs > 1);
// Copy final settings.
MOZ_ASSERT((try_run_size >> gPageSize2Pow) <= UINT8_MAX);
mRunSizePages = static_cast<uint8_t>(try_run_size >> gPageSize2Pow);
mRunNumRegions = try_nregs;
mRunNumRegionsMask = try_mask_nelms;
mRunFirstRegionOffset = try_reg0_offset;
mSizeDivisor = FastDivisor<uint16_t>(aSizeClass.Size(), try_run_size);
}
void arena_t::ResetSmallAllocRandomization() {
if (MOZ_UNLIKELY(opt_randomize_small)) {
MaybeMutexAutoLock lock(mLock);
InitPRNG();
}
mRandomizeSmallAllocations = opt_randomize_small;
}
void arena_t::InitPRNG() {
// Both another thread could race and the code backing RandomUint64
// (arc4random for example) may allocate memory while here, so we must
// ensure to start the mPRNG initialization only once and to not hold
// the lock while initializing.
mIsPRNGInitializing = true;
{
mLock.Unlock();
mozilla::Maybe<uint64_t> prngState1 = mozilla::RandomUint64();
mozilla::Maybe<uint64_t> prngState2 = mozilla::RandomUint64();
mLock.Lock();
mozilla::non_crypto::XorShift128PlusRNG prng(prngState1.valueOr(0),
prngState2.valueOr(0));
if (mPRNG) {
*mPRNG = prng;
} else {
void* backing =
base_alloc(sizeof(mozilla::non_crypto::XorShift128PlusRNG));
mPRNG = new (backing)
mozilla::non_crypto::XorShift128PlusRNG(std::move(prng));
}
}
mIsPRNGInitializing = false;
}
void* arena_t::MallocSmall(size_t aSize, bool aZero) {
void* ret;
arena_bin_t* bin;
arena_run_t* run;
SizeClass sizeClass(aSize);
aSize = sizeClass.Size();
switch (sizeClass.Type()) {
case SizeClass::Tiny:
bin = &mBins[FloorLog2(aSize / kMinTinyClass)];
break;
case SizeClass::Quantum:
// Although we divide 2 things by kQuantum, the compiler will
// reduce `kMinQuantumClass / kQuantum` and `kNumTinyClasses` to a
// single constant.
bin = &mBins[kNumTinyClasses + (aSize / kQuantum) -
(kMinQuantumClass / kQuantum)];
break;
case SizeClass::QuantumWide:
bin =
&mBins[kNumTinyClasses + kNumQuantumClasses + (aSize / kQuantumWide) -
(kMinQuantumWideClass / kQuantumWide)];
break;
case SizeClass::SubPage:
bin =
&mBins[kNumTinyClasses + kNumQuantumClasses + kNumQuantumWideClasses +
(FloorLog2(aSize) - LOG2(kMinSubPageClass))];
break;
default:
MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unexpected size class type");
}
MOZ_DIAGNOSTIC_ASSERT(aSize == bin->mSizeClass);
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
#ifdef MOZ_DEBUG
bool isInitializingThread(false);
#endif
if (MOZ_UNLIKELY(mRandomizeSmallAllocations && mPRNG == nullptr &&
!mIsPRNGInitializing)) {
#ifdef MOZ_DEBUG
isInitializingThread = true;
#endif
InitPRNG();
}
MOZ_ASSERT(!mRandomizeSmallAllocations || mPRNG ||
(mIsPRNGInitializing && !isInitializingThread));
num_dirty_before = mNumDirty;
run = GetNonFullBinRun(bin);
num_dirty_after = mNumDirty;
if (MOZ_UNLIKELY(!run)) {
return nullptr;
}
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
MOZ_DIAGNOSTIC_ASSERT(run->mNumFree > 0);
ret = ArenaRunRegAlloc(run, bin);
MOZ_DIAGNOSTIC_ASSERT(ret);
run->mNumFree--;
if (!ret) {
return nullptr;
}
mStats.allocated_small += aSize;
mStats.operations++;
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
if (!aZero) {
ApplyZeroOrJunk(ret, aSize);
} else {
memset(ret, 0, aSize);
}
return ret;
}
void* arena_t::MallocLarge(size_t aSize, bool aZero) {
void* ret;
// Large allocation.
aSize = PAGE_CEILING(aSize);
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
num_dirty_before = mNumDirty;
ret = AllocRun(aSize, true, aZero);
num_dirty_after = mNumDirty;
if (!ret) {
return nullptr;
}
mStats.allocated_large += aSize;
mStats.operations++;
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
if (!aZero) {
ApplyZeroOrJunk(ret, aSize);
}
return ret;
}
void* arena_t::Malloc(size_t aSize, bool aZero) {
MOZ_DIAGNOSTIC_ASSERT(mMagic == ARENA_MAGIC);
MOZ_ASSERT(aSize != 0);
if (aSize <= gMaxBinClass) {
return MallocSmall(aSize, aZero);
}
if (aSize <= gMaxLargeClass) {
return MallocLarge(aSize, aZero);
}
return MallocHuge(aSize, aZero);
}
// Only handles large allocations that require more than page alignment.
void* arena_t::PallocLarge(size_t aAlignment, size_t aSize, size_t aAllocSize) {
void* ret;
size_t offset;
arena_chunk_t* chunk;
MOZ_ASSERT((aSize & gPageSizeMask) == 0);
MOZ_ASSERT((aAlignment & gPageSizeMask) == 0);
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
num_dirty_before = mNumDirty;
ret = AllocRun(aAllocSize, true, false);
if (!ret) {
return nullptr;
}
chunk = GetChunkForPtr(ret);
offset = uintptr_t(ret) & (aAlignment - 1);
MOZ_ASSERT((offset & gPageSizeMask) == 0);
MOZ_ASSERT(offset < aAllocSize);
if (offset == 0) {
TrimRunTail(chunk, (arena_run_t*)ret, aAllocSize, aSize, false);
} else {
size_t leadsize, trailsize;
leadsize = aAlignment - offset;
if (leadsize > 0) {
TrimRunHead(chunk, (arena_run_t*)ret, aAllocSize,
aAllocSize - leadsize);
ret = (void*)(uintptr_t(ret) + leadsize);
}
trailsize = aAllocSize - leadsize - aSize;
if (trailsize != 0) {
// Trim trailing space.
MOZ_ASSERT(trailsize < aAllocSize);
TrimRunTail(chunk, (arena_run_t*)ret, aSize + trailsize, aSize, false);
}
}
num_dirty_after = mNumDirty;
mStats.allocated_large += aSize;
mStats.operations++;
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
// Note that since Bug 1488780we don't attempt purge dirty memory on this code
// path. In general there won't be dirty memory above the threshold after an
// allocation, only after free. The exception is if the dirty page threshold
// has changed.
ApplyZeroOrJunk(ret, aSize);
return ret;
}
void* arena_t::Palloc(size_t aAlignment, size_t aSize) {
void* ret;
size_t ceil_size;
// Round size up to the nearest multiple of alignment.
//
// This done, we can take advantage of the fact that for each small
// size class, every object is aligned at the smallest power of two
// that is non-zero in the base two representation of the size. For
// example:
//
// Size | Base 2 | Minimum alignment
// -----+----------+------------------
// 96 | 1100000 | 32
// 144 | 10100000 | 32
// 192 | 11000000 | 64
//
// Depending on runtime settings, it is possible that arena_malloc()
// will further round up to a power of two, but that never causes
// correctness issues.
ceil_size = ALIGNMENT_CEILING(aSize, aAlignment);
// (ceil_size < aSize) protects against the combination of maximal
// alignment and size greater than maximal alignment.
if (ceil_size < aSize) {
// size_t overflow.
return nullptr;
}
if (ceil_size <= gPageSize ||
(aAlignment <= gPageSize && ceil_size <= gMaxLargeClass)) {
ret = Malloc(ceil_size, false);
} else {
size_t run_size;
// We can't achieve sub-page alignment, so round up alignment
// permanently; it makes later calculations simpler.
aAlignment = PAGE_CEILING(aAlignment);
ceil_size = PAGE_CEILING(aSize);
// (ceil_size < aSize) protects against very large sizes within
// pagesize of SIZE_T_MAX.
//
// (ceil_size + aAlignment < ceil_size) protects against the
// combination of maximal alignment and ceil_size large enough
// to cause overflow. This is similar to the first overflow
// check above, but it needs to be repeated due to the new
// ceil_size value, which may now be *equal* to maximal
// alignment, whereas before we only detected overflow if the
// original size was *greater* than maximal alignment.
if (ceil_size < aSize || ceil_size + aAlignment < ceil_size) {
// size_t overflow.
return nullptr;
}
// Calculate the size of the over-size run that arena_palloc()
// would need to allocate in order to guarantee the alignment.
if (ceil_size >= aAlignment) {
run_size = ceil_size + aAlignment - gPageSize;
} else {
// It is possible that (aAlignment << 1) will cause
// overflow, but it doesn't matter because we also
// subtract pagesize, which in the case of overflow
// leaves us with a very large run_size. That causes
// the first conditional below to fail, which means
// that the bogus run_size value never gets used for
// anything important.
run_size = (aAlignment << 1) - gPageSize;
}
if (run_size <= gMaxLargeClass) {
ret = PallocLarge(aAlignment, ceil_size, run_size);
} else if (aAlignment <= kChunkSize) {
ret = MallocHuge(ceil_size, false);
} else {
ret = PallocHuge(ceil_size, aAlignment, false);
}
}
MOZ_ASSERT((uintptr_t(ret) & (aAlignment - 1)) == 0);
return ret;
}
class AllocInfo {
public:
template <bool Validate = false>
static inline AllocInfo Get(const void* aPtr) {
// If the allocator is not initialized, the pointer can't belong to it.
if (Validate && !malloc_initialized) {
return AllocInfo();
}
auto chunk = GetChunkForPtr(aPtr);
if (Validate) {
if (!chunk || !gChunkRTree.Get(chunk)) {
return AllocInfo();
}
}
if (chunk != aPtr) {
MOZ_DIAGNOSTIC_ASSERT(chunk->arena->mMagic == ARENA_MAGIC);
size_t pageind = (((uintptr_t)aPtr - (uintptr_t)chunk) >> gPageSize2Pow);
return GetInChunk(aPtr, chunk, pageind);
}
extent_node_t key;
// Huge allocation
key.mAddr = chunk;
MutexAutoLock lock(huge_mtx);
extent_node_t* node = huge.Search(&key);
if (Validate && !node) {
return AllocInfo();
}
return AllocInfo(node->mSize, node);
}
// Get the allocation information for a pointer we know is within a chunk
// (Small or large, not huge).
static inline AllocInfo GetInChunk(const void* aPtr, arena_chunk_t* aChunk,
size_t pageind) {
size_t mapbits = aChunk->map[pageind].bits;
MOZ_DIAGNOSTIC_ASSERT((mapbits & CHUNK_MAP_ALLOCATED) != 0);
size_t size;
if ((mapbits & CHUNK_MAP_LARGE) == 0) {
arena_run_t* run = (arena_run_t*)(mapbits & ~gPageSizeMask);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
size = run->mBin->mSizeClass;
} else {
size = mapbits & ~gPageSizeMask;
MOZ_DIAGNOSTIC_ASSERT(size != 0);
}
return AllocInfo(size, aChunk);
}
// Validate ptr before assuming that it points to an allocation. Currently,
// the following validation is performed:
//
// + Check that ptr is not nullptr.
//
// + Check that ptr lies within a mapped chunk.
static inline AllocInfo GetValidated(const void* aPtr) {
return Get<true>(aPtr);
}
AllocInfo() : mSize(0), mChunk(nullptr) {}
explicit AllocInfo(size_t aSize, arena_chunk_t* aChunk)
: mSize(aSize), mChunk(aChunk) {
MOZ_ASSERT(mSize <= gMaxLargeClass);
}
explicit AllocInfo(size_t aSize, extent_node_t* aNode)
: mSize(aSize), mNode(aNode) {
MOZ_ASSERT(mSize > gMaxLargeClass);
}
size_t Size() { return mSize; }
arena_t* Arena() {
if (mSize <= gMaxLargeClass) {
return mChunk->arena;
}
// Best effort detection that we're not trying to access an already
// disposed arena. In the case of a disposed arena, the memory location
// pointed by mNode->mArena is either free (but still a valid memory
// region, per TypedBaseAlloc<arena_t>), in which case its id was reset,
// or has been reallocated for a new region, and its id is very likely
// different (per randomness). In both cases, the id is unlikely to
// match what it was for the disposed arena.
MOZ_RELEASE_ASSERT(mNode->mArenaId == mNode->mArena->mId);
return mNode->mArena;
}
bool IsValid() const { return !!mSize; }
private:
size_t mSize;
union {
// Pointer to the chunk associated with the allocation for small
// and large allocations.
arena_chunk_t* mChunk;
// Pointer to the extent node for huge allocations.
extent_node_t* mNode;
};
};
inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
jemalloc_ptr_info_t* aInfo) {
arena_chunk_t* chunk = GetChunkForPtr(aPtr);
// Is the pointer null, or within one chunk's size of null?
// Alternatively, if the allocator is not initialized yet, the pointer
// can't be known.
if (!chunk || !malloc_initialized) {
*aInfo = {TagUnknown, nullptr, 0, 0};
return;
}
// Look for huge allocations before looking for |chunk| in gChunkRTree.
// This is necessary because |chunk| won't be in gChunkRTree if it's
// the second or subsequent chunk in a huge allocation.
extent_node_t* node;
extent_node_t key;
{
MutexAutoLock lock(huge_mtx);
key.mAddr = const_cast<void*>(aPtr);
node =
reinterpret_cast<RedBlackTree<extent_node_t, ExtentTreeBoundsTrait>*>(
&huge)
->Search(&key);
if (node) {
*aInfo = {TagLiveAlloc, node->mAddr, node->mSize, node->mArena->mId};
return;
}
}
// It's not a huge allocation. Check if we have a known chunk.
if (!gChunkRTree.Get(chunk)) {
*aInfo = {TagUnknown, nullptr, 0, 0};
return;
}
MOZ_DIAGNOSTIC_ASSERT(chunk->arena->mMagic == ARENA_MAGIC);
// Get the page number within the chunk.
size_t pageind = (((uintptr_t)aPtr - (uintptr_t)chunk) >> gPageSize2Pow);
if (pageind < gChunkHeaderNumPages) {
// Within the chunk header.
*aInfo = {TagUnknown, nullptr, 0, 0};
return;
}
size_t mapbits = chunk->map[pageind].bits;
if (!(mapbits & CHUNK_MAP_ALLOCATED)) {
void* pageaddr = (void*)(uintptr_t(aPtr) & ~gPageSizeMask);
*aInfo = {TagFreedPage, pageaddr, gPageSize, chunk->arena->mId};
return;
}
if (mapbits & CHUNK_MAP_LARGE) {
// It's a large allocation. Only the first page of a large
// allocation contains its size, so if the address is not in
// the first page, scan back to find the allocation size.
size_t size;
while (true) {
size = mapbits & ~gPageSizeMask;
if (size != 0) {
break;
}
// The following two return paths shouldn't occur in
// practice unless there is heap corruption.
pageind--;
MOZ_DIAGNOSTIC_ASSERT(pageind >= gChunkHeaderNumPages);
if (pageind < gChunkHeaderNumPages) {
*aInfo = {TagUnknown, nullptr, 0, 0};
return;
}
mapbits = chunk->map[pageind].bits;
MOZ_DIAGNOSTIC_ASSERT(mapbits & CHUNK_MAP_LARGE);
if (!(mapbits & CHUNK_MAP_LARGE)) {
*aInfo = {TagUnknown, nullptr, 0, 0};
return;
}
}
void* addr = ((char*)chunk) + (pageind << gPageSize2Pow);
*aInfo = {TagLiveAlloc, addr, size, chunk->arena->mId};
return;
}
// It must be a small allocation.
auto run = (arena_run_t*)(mapbits & ~gPageSizeMask);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
// The allocation size is stored in the run metadata.
size_t size = run->mBin->mSizeClass;
// Address of the first possible pointer in the run after its headers.
uintptr_t reg0_addr = (uintptr_t)run + run->mBin->mRunFirstRegionOffset;
if (aPtr < (void*)reg0_addr) {
// In the run header.
*aInfo = {TagUnknown, nullptr, 0, 0};
return;
}
// Position in the run.
unsigned regind = ((uintptr_t)aPtr - reg0_addr) / size;
// Pointer to the allocation's base address.
void* addr = (void*)(reg0_addr + regind * size);
// Check if the allocation has been freed.
unsigned elm = regind >> (LOG2(sizeof(int)) + 3);
unsigned bit = regind - (elm << (LOG2(sizeof(int)) + 3));
PtrInfoTag tag =
((run->mRegionsMask[elm] & (1U << bit))) ? TagFreedAlloc : TagLiveAlloc;
*aInfo = {tag, addr, size, chunk->arena->mId};
}
namespace Debug {
// Helper for debuggers. We don't want it to be inlined and optimized out.
MOZ_NEVER_INLINE jemalloc_ptr_info_t* jemalloc_ptr_info(const void* aPtr) {
static jemalloc_ptr_info_t info;
MozJemalloc::jemalloc_ptr_info(aPtr, &info);
return &info;
}
} // namespace Debug
arena_chunk_t* arena_t::DallocSmall(arena_chunk_t* aChunk, void* aPtr,
arena_chunk_map_t* aMapElm) {
arena_run_t* run;
arena_bin_t* bin;
size_t size;
run = (arena_run_t*)(aMapElm->bits & ~gPageSizeMask);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
bin = run->mBin;
size = bin->mSizeClass;
MOZ_DIAGNOSTIC_ASSERT(uintptr_t(aPtr) >=
uintptr_t(run) + bin->mRunFirstRegionOffset);
arena_run_reg_dalloc(run, bin, aPtr, size);
run->mNumFree++;
arena_chunk_t* dealloc_chunk = nullptr;
if (run->mNumFree == bin->mRunNumRegions) {
// This run is entirely freed, remove it from our bin.
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
run->mMagic = 0;
#endif
MOZ_ASSERT(bin->mNonFullRuns.ElementProbablyInList(run));
bin->mNonFullRuns.remove(run);
dealloc_chunk = DallocRun(run, true);
bin->mNumRuns--;
} else if (run->mNumFree == 1) {
// This is first slot we freed from this run, start tracking.
MOZ_ASSERT(!bin->mNonFullRuns.ElementProbablyInList(run));
bin->mNonFullRuns.pushFront(run);
}
// else we just keep the run in mNonFullRuns where it is.
// Note that we could move it to the head of the list here to get a strict
// "most-recently-freed" order, but some of our benchmarks seem to be more
// sensible to the increased overhead that this brings than to the order
// supposedly slightly better for keeping CPU caches warm if we do.
// In general we cannot foresee the future, so any order we choose might
// perform different for different use cases and needs to be balanced with
// the book-keeping overhead via measurements.
mStats.allocated_small -= size;
mStats.operations++;
return dealloc_chunk;
}
arena_chunk_t* arena_t::DallocLarge(arena_chunk_t* aChunk, void* aPtr) {
MOZ_DIAGNOSTIC_ASSERT((uintptr_t(aPtr) & gPageSizeMask) == 0);
size_t pageind = (uintptr_t(aPtr) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t size = aChunk->map[pageind].bits & ~gPageSizeMask;
mStats.allocated_large -= size;
mStats.operations++;
return DallocRun((arena_run_t*)aPtr, true);
}
static inline void arena_dalloc(void* aPtr, size_t aOffset, arena_t* aArena) {
MOZ_ASSERT(aPtr);
MOZ_ASSERT(aOffset != 0);
MOZ_ASSERT(GetChunkOffsetForPtr(aPtr) == aOffset);
auto chunk = (arena_chunk_t*)((uintptr_t)aPtr - aOffset);
auto arena = chunk->arena;
MOZ_ASSERT(arena);
MOZ_DIAGNOSTIC_ASSERT(arena->mMagic == ARENA_MAGIC);
MOZ_RELEASE_ASSERT(!aArena || arena == aArena);
size_t pageind = aOffset >> gPageSize2Pow;
if (opt_poison) {
AllocInfo info = AllocInfo::GetInChunk(aPtr, chunk, pageind);
MOZ_ASSERT(info.IsValid());
MaybePoison(aPtr, info.Size());
}
arena_chunk_t* chunk_dealloc_delay = nullptr;
purge_action_t purge_action;
{
MOZ_DIAGNOSTIC_ASSERT(arena->mLock.SafeOnThisThread());
MaybeMutexAutoLock lock(arena->mLock);
arena_chunk_map_t* mapelm = &chunk->map[pageind];
MOZ_RELEASE_ASSERT(
(mapelm->bits &
(CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED | CHUNK_MAP_ZEROED)) == 0,
"Freeing in a page with bad bits.");
MOZ_RELEASE_ASSERT((mapelm->bits & CHUNK_MAP_ALLOCATED) != 0,
"Double-free?");
if ((mapelm->bits & CHUNK_MAP_LARGE) == 0) {
// Small allocation.
chunk_dealloc_delay = arena->DallocSmall(chunk, aPtr, mapelm);
} else {
// Large allocation.
chunk_dealloc_delay = arena->DallocLarge(chunk, aPtr);
}
purge_action = arena->ShouldStartPurge();
}
if (chunk_dealloc_delay) {
chunk_dealloc((void*)chunk_dealloc_delay, kChunkSize, ARENA_CHUNK);
}
arena->MayDoOrQueuePurge(purge_action);
}
static inline void idalloc(void* ptr, arena_t* aArena) {
size_t offset;
MOZ_ASSERT(ptr);
offset = GetChunkOffsetForPtr(ptr);
if (offset != 0) {
arena_dalloc(ptr, offset, aArena);
} else {
huge_dalloc(ptr, aArena);
}
}
inline purge_action_t arena_t::ShouldStartPurge() {
if (mNumDirty > mMaxDirty) {
if (!mIsDeferredPurgeEnabled) {
return purge_action_t::PurgeNow;
}
if (mIsPurgePending) {
return purge_action_t::None;
}
mIsPurgePending = true;
return purge_action_t::Queue;
}
return purge_action_t::None;
}
inline void arena_t::MayDoOrQueuePurge(purge_action_t aAction) {
switch (aAction) {
case purge_action_t::Queue:
// Note that this thread committed earlier by setting
// mIsDeferredPurgePending to add us to the list. There is a low
// chance that in the meantime another thread ran Purge() and cleared
// the flag, but that is fine, we'll adjust our bookkeeping when calling
// ShouldStartPurge() or Purge() next time.
gArenas.AddToOutstandingPurges(this);
break;
case purge_action_t::PurgeNow:
PurgeResult pr;
do {
pr = Purge(PurgeIfThreshold);
} while (pr == arena_t::PurgeResult::Continue);
// Arenas cannot die here because the caller is still using the arena, if
// they did it'd be a use-after-free: the arena is destroyed but then used
// afterwards.
MOZ_RELEASE_ASSERT(pr != arena_t::PurgeResult::Dying);
break;
case purge_action_t::None:
// do nothing.
break;
}
}
inline void arena_t::NotifySignificantReuse() {
// Note that there is a chance here for a race between threads calling
// GetTimeStampNS in a different order than writing it to the Atomic,
// resulting in mLastSignificantReuseNS going potentially backwards.
// Our use case is not sensitive to small deviations, the worse that can
// happen is a slightly earlier purge.
mLastSignificantReuseNS = GetTimestampNS();
}
void arena_t::RallocShrinkLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
size_t aOldSize) {
MOZ_ASSERT(aSize < aOldSize);
// Shrink the run, and make trailing pages available for other
// allocations.
purge_action_t purge_action;
{
MaybeMutexAutoLock lock(mLock);
TrimRunTail(aChunk, (arena_run_t*)aPtr, aOldSize, aSize, true);
mStats.allocated_large -= aOldSize - aSize;
mStats.operations++;
purge_action = ShouldStartPurge();
}
MayDoOrQueuePurge(purge_action);
}
// Returns whether reallocation was successful.
bool arena_t::RallocGrowLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
size_t aOldSize) {
size_t pageind = (uintptr_t(aPtr) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t npages = aOldSize >> gPageSize2Pow;
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
MOZ_DIAGNOSTIC_ASSERT(aOldSize ==
(aChunk->map[pageind].bits & ~gPageSizeMask));
// Try to extend the run.
MOZ_ASSERT(aSize > aOldSize);
if (pageind + npages < gChunkNumPages - 1 &&
(aChunk->map[pageind + npages].bits &
(CHUNK_MAP_ALLOCATED | CHUNK_MAP_BUSY)) == 0 &&
(aChunk->map[pageind + npages].bits & ~gPageSizeMask) >=
aSize - aOldSize) {
num_dirty_before = mNumDirty;
// The next run is available and sufficiently large. Split the
// following run, then merge the first part with the existing
// allocation.
if (!SplitRun((arena_run_t*)(uintptr_t(aChunk) +
((pageind + npages) << gPageSize2Pow)),
aSize - aOldSize, true, false)) {
return false;
}
aChunk->map[pageind].bits = aSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
aChunk->map[pageind + npages].bits =
CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
mStats.allocated_large += aSize - aOldSize;
mStats.operations++;
num_dirty_after = mNumDirty;
} else {
return false;
}
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
return true;
}
void* arena_t::RallocSmallOrLarge(void* aPtr, size_t aSize, size_t aOldSize) {
void* ret;
size_t copysize;
SizeClass sizeClass(aSize);
// Try to avoid moving the allocation.
if (aOldSize <= gMaxLargeClass && sizeClass.Size() == aOldSize) {
if (aSize < aOldSize) {
MaybePoison((void*)(uintptr_t(aPtr) + aSize), aOldSize - aSize);
}
return aPtr;
}
if (sizeClass.Type() == SizeClass::Large && aOldSize > gMaxBinClass &&
aOldSize <= gMaxLargeClass) {
arena_chunk_t* chunk = GetChunkForPtr(aPtr);
if (sizeClass.Size() < aOldSize) {
// Fill before shrinking in order to avoid a race.
MaybePoison((void*)((uintptr_t)aPtr + aSize), aOldSize - aSize);
RallocShrinkLarge(chunk, aPtr, sizeClass.Size(), aOldSize);
return aPtr;
}
if (RallocGrowLarge(chunk, aPtr, sizeClass.Size(), aOldSize)) {
ApplyZeroOrJunk((void*)((uintptr_t)aPtr + aOldSize), aSize - aOldSize);
return aPtr;
}
}
// If we get here, then aSize and aOldSize are different enough that we
// need to move the object or the run can't be expanded because the memory
// after it is allocated or busy. In that case, fall back to allocating new
// space and copying. Allow non-private arenas to switch arenas.
ret = (mIsPrivate ? this : choose_arena(aSize))->Malloc(aSize, false);
if (!ret) {
return nullptr;
}
// Junk/zero-filling were already done by arena_t::Malloc().
copysize = (aSize < aOldSize) ? aSize : aOldSize;
#ifdef VM_COPY_MIN
if (copysize >= VM_COPY_MIN) {
pages_copy(ret, aPtr, copysize);
} else
#endif
{
memcpy(ret, aPtr, copysize);
}
idalloc(aPtr, this);
return ret;
}
void* arena_t::Ralloc(void* aPtr, size_t aSize, size_t aOldSize) {
MOZ_DIAGNOSTIC_ASSERT(mMagic == ARENA_MAGIC);
MOZ_ASSERT(aPtr);
MOZ_ASSERT(aSize != 0);
return (aSize <= gMaxLargeClass) ? RallocSmallOrLarge(aPtr, aSize, aOldSize)
: RallocHuge(aPtr, aSize, aOldSize);
}
void* arena_t::operator new(size_t aCount, const fallible_t&) noexcept {
MOZ_ASSERT(aCount == sizeof(arena_t));
return TypedBaseAlloc<arena_t>::alloc();
}
void arena_t::operator delete(void* aPtr) {
TypedBaseAlloc<arena_t>::dealloc((arena_t*)aPtr);
}
arena_t::arena_t(arena_params_t* aParams, bool aIsPrivate) {
unsigned i;
memset(&mLink, 0, sizeof(mLink));
memset(&mStats, 0, sizeof(arena_stats_t));
mId = 0;
// Initialize chunks.
mChunksDirty.Init();
#ifdef MALLOC_DOUBLE_PURGE
new (&mChunksMAdvised) DoublyLinkedList<arena_chunk_t>();
#endif
mSpare = nullptr;
mRandomizeSmallAllocations = opt_randomize_small;
MaybeMutex::DoLock doLock = MaybeMutex::MUST_LOCK;
if (aParams) {
uint32_t randFlags = aParams->mFlags & ARENA_FLAG_RANDOMIZE_SMALL_MASK;
switch (randFlags) {
case ARENA_FLAG_RANDOMIZE_SMALL_ENABLED:
mRandomizeSmallAllocations = true;
break;
case ARENA_FLAG_RANDOMIZE_SMALL_DISABLED:
mRandomizeSmallAllocations = false;
break;
case ARENA_FLAG_RANDOMIZE_SMALL_DEFAULT:
default:
break;
}
uint32_t threadFlags = aParams->mFlags & ARENA_FLAG_THREAD_MASK;
if (threadFlags == ARENA_FLAG_THREAD_MAIN_THREAD_ONLY) {
// At the moment we require that any ARENA_FLAG_THREAD_MAIN_THREAD_ONLY
// arenas are created and therefore always accessed by the main thread.
// This is for two reasons:
// * it allows jemalloc_stats to read their statistics (we also require
// that jemalloc_stats is only used on the main thread).
// * Only main-thread or threadsafe arenas can be guanteed to be in a
// consistent state after a fork() from the main thread. If fork()
// occurs off-thread then the new child process cannot use these arenas
// (new children should usually exec() or exit() since other data may
// also be inconsistent).
MOZ_ASSERT(gArenas.IsOnMainThread());
MOZ_ASSERT(aIsPrivate);
doLock = MaybeMutex::AVOID_LOCK_UNSAFE;
}
mMaxDirtyIncreaseOverride = aParams->mMaxDirtyIncreaseOverride;
mMaxDirtyDecreaseOverride = aParams->mMaxDirtyDecreaseOverride;
} else {
mMaxDirtyIncreaseOverride = 0;
mMaxDirtyDecreaseOverride = 0;
}
mLastSignificantReuseNS = GetTimestampNS();
mIsPurgePending = false;
mIsDeferredPurgeEnabled = gArenas.IsDeferredPurgeEnabled();
MOZ_RELEASE_ASSERT(mLock.Init(doLock));
mPRNG = nullptr;
mIsPRNGInitializing = false;
mIsPrivate = aIsPrivate;
mNumDirty = 0;
mNumFresh = 0;
mNumMAdvised = 0;
// The default maximum amount of dirty pages allowed on arenas is a fraction
// of opt_dirty_max.
mMaxDirtyBase = (aParams && aParams->mMaxDirty) ? aParams->mMaxDirty
: (opt_dirty_max / 8);
UpdateMaxDirty();
mRunsAvail.Init();
// Initialize bins.
SizeClass sizeClass(1);
for (i = 0;; i++) {
arena_bin_t& bin = mBins[i];
bin.Init(sizeClass);
// SizeClass doesn't want sizes larger than gMaxBinClass for now.
if (sizeClass.Size() == gMaxBinClass) {
break;
}
sizeClass = sizeClass.Next();
}
MOZ_ASSERT(i == NUM_SMALL_CLASSES - 1);
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
mMagic = ARENA_MAGIC;
#endif
}
arena_t::~arena_t() {
size_t i;
MaybeMutexAutoLock lock(mLock);
MOZ_RELEASE_ASSERT(!mLink.Left() && !mLink.Right(),
"Arena is still registered");
MOZ_RELEASE_ASSERT(!mStats.allocated_small && !mStats.allocated_large,
"Arena is not empty");
if (mSpare) {
chunk_dealloc(mSpare, kChunkSize, ARENA_CHUNK);
}
for (i = 0; i < NUM_SMALL_CLASSES; i++) {
MOZ_RELEASE_ASSERT(mBins[i].mNonFullRuns.isEmpty(), "Bin is not empty");
}
#ifdef MOZ_DEBUG
{
MutexAutoLock lock(huge_mtx);
// This is an expensive check, so we only do it on debug builds.
for (auto node : huge.iter()) {
MOZ_RELEASE_ASSERT(node->mArenaId != mId, "Arena has huge allocations");
}
}
#endif
mId = 0;
}
arena_t* ArenaCollection::CreateArena(bool aIsPrivate,
arena_params_t* aParams) {
arena_t* ret = new (fallible) arena_t(aParams, aIsPrivate);
if (!ret) {
// Only reached if there is an OOM error.
// OOM here is quite inconvenient to propagate, since dealing with it
// would require a check for failure in the fast path. Instead, punt
// by using the first arena.
// In practice, this is an extremely unlikely failure.
_malloc_message(_getprogname(), ": (malloc) Error initializing arena\n");
return mDefaultArena;
}
MutexAutoLock lock(mLock);
// For public arenas, it's fine to just use incrementing arena id
if (!aIsPrivate) {
ret->mId = mLastPublicArenaId++;
mArenas.Insert(ret);
return ret;
}
#ifdef NON_RANDOM_ARENA_IDS
// For private arenas, slightly obfuscate the id by XORing a key generated
// once, and rotate the bits by an amount also generated once.
if (mArenaIdKey == 0) {
mozilla::Maybe<uint64_t> maybeRandom = mozilla::RandomUint64();
MOZ_RELEASE_ASSERT(maybeRandom.isSome());
mArenaIdKey = maybeRandom.value();
maybeRandom = mozilla::RandomUint64();
MOZ_RELEASE_ASSERT(maybeRandom.isSome());
mArenaIdRotation = maybeRandom.value() & (sizeof(void*) * 8 - 1);
}
arena_id_t id = reinterpret_cast<arena_id_t>(ret) ^ mArenaIdKey;
ret->mId =
(id >> mArenaIdRotation) | (id << (sizeof(void*) * 8 - mArenaIdRotation));
mPrivateArenas.Insert(ret);
return ret;
#else
// For private arenas, generate a cryptographically-secure random id for the
// new arena. If an attacker manages to get control of the process, this
// should make it more difficult for them to "guess" the ID of a memory
// arena, stopping them from getting data they may want
Tree& tree = (ret->IsMainThreadOnly()) ? mMainThreadArenas : mPrivateArenas;
arena_id_t arena_id;
do {
arena_id = MakeRandArenaId(ret->IsMainThreadOnly());
// Keep looping until we ensure that the random number we just generated
// isn't already in use by another active arena
} while (GetByIdInternal(tree, arena_id));
ret->mId = arena_id;
tree.Insert(ret);
return ret;
#endif
}
#ifndef NON_RANDOM_ARENA_IDS
arena_id_t ArenaCollection::MakeRandArenaId(bool aIsMainThreadOnly) const {
uint64_t rand;
do {
mozilla::Maybe<uint64_t> maybeRandomId = mozilla::RandomUint64();
MOZ_RELEASE_ASSERT(maybeRandomId.isSome());
rand = maybeRandomId.value();
// Set or clear the least significant bit depending on if this is a
// main-thread-only arena. We use this in GetById.
if (aIsMainThreadOnly) {
rand = rand | MAIN_THREAD_ARENA_BIT;
} else {
rand = rand & ~MAIN_THREAD_ARENA_BIT;
}
// Avoid 0 as an arena Id. We use 0 for disposed arenas.
} while (rand == 0);
return arena_id_t(rand);
}
#endif
// End arena.
// ***************************************************************************
// Begin general internal functions.
// Initialize huge allocation data.
static void huge_init() MOZ_REQUIRES(gInitLock) {
huge_mtx.Init();
MOZ_PUSH_IGNORE_THREAD_SAFETY
huge.Init();
huge_allocated = 0;
huge_mapped = 0;
huge_operations = 0;
MOZ_POP_THREAD_SAFETY
}
void* arena_t::MallocHuge(size_t aSize, bool aZero) {
return PallocHuge(aSize, kChunkSize, aZero);
}
void* arena_t::PallocHuge(size_t aSize, size_t aAlignment, bool aZero) {
void* ret;
size_t csize;
size_t psize;
extent_node_t* node;
// We're going to configure guard pages in the region between the
// page-aligned size and the chunk-aligned size, so if those are the same
// then we need to force that region into existence.
csize = CHUNK_CEILING(aSize + gPageSize);
if (csize < aSize) {
// size is large enough to cause size_t wrap-around.
return nullptr;
}
// Allocate an extent node with which to track the chunk.
node = ExtentAlloc::alloc();
if (!node) {
return nullptr;
}
// Allocate one or more contiguous chunks for this request.
ret = chunk_alloc(csize, aAlignment, false);
if (!ret) {
ExtentAlloc::dealloc(node);
return nullptr;
}
psize = PAGE_CEILING(aSize);
#ifdef MOZ_DEBUG
if (aZero) {
chunk_assert_zero(ret, psize);
}
#endif
// Insert node into huge.
node->mAddr = ret;
node->mSize = psize;
node->mArena = this;
node->mArenaId = mId;
{
MutexAutoLock lock(huge_mtx);
huge.Insert(node);
// Although we allocated space for csize bytes, we indicate that we've
// allocated only psize bytes.
//
// If DECOMMIT is defined, this is a reasonable thing to do, since
// we'll explicitly decommit the bytes in excess of psize.
//
// If DECOMMIT is not defined, then we're relying on the OS to be lazy
// about how it allocates physical pages to mappings. If we never
// touch the pages in excess of psize, the OS won't allocate a physical
// page, and we won't use more than psize bytes of physical memory.
//
// A correct program will only touch memory in excess of how much it
// requested if it first calls malloc_usable_size and finds out how
// much space it has to play with. But because we set node->mSize =
// psize above, malloc_usable_size will return psize, not csize, and
// the program will (hopefully) never touch bytes in excess of psize.
// Thus those bytes won't take up space in physical memory, and we can
// reasonably claim we never "allocated" them in the first place.
huge_allocated += psize;
huge_mapped += csize;
huge_operations++;
}
pages_decommit((void*)((uintptr_t)ret + psize), csize - psize);
if (!aZero) {
ApplyZeroOrJunk(ret, psize);
}
return ret;
}
void* arena_t::RallocHuge(void* aPtr, size_t aSize, size_t aOldSize) {
void* ret;
size_t copysize;
// Avoid moving the allocation if the size class would not change.
if (aOldSize > gMaxLargeClass &&
CHUNK_CEILING(aSize + gPageSize) == CHUNK_CEILING(aOldSize + gPageSize)) {
size_t psize = PAGE_CEILING(aSize);
if (aSize < aOldSize) {
MaybePoison((void*)((uintptr_t)aPtr + aSize), aOldSize - aSize);
}
if (psize < aOldSize) {
extent_node_t key;
pages_decommit((void*)((uintptr_t)aPtr + psize), aOldSize - psize);
// Update recorded size.
MutexAutoLock lock(huge_mtx);
key.mAddr = const_cast<void*>(aPtr);
extent_node_t* node = huge.Search(&key);
MOZ_ASSERT(node);
MOZ_ASSERT(node->mSize == aOldSize);
MOZ_RELEASE_ASSERT(node->mArena == this);
huge_allocated -= aOldSize - psize;
huge_operations++;
// No need to change huge_mapped, because we didn't (un)map anything.
node->mSize = psize;
} else if (psize > aOldSize) {
if (!pages_commit((void*)((uintptr_t)aPtr + aOldSize),
psize - aOldSize)) {
return nullptr;
}
// We need to update the recorded size if the size increased,
// so malloc_usable_size doesn't return a value smaller than
// what was requested via realloc().
extent_node_t key;
MutexAutoLock lock(huge_mtx);
key.mAddr = const_cast<void*>(aPtr);
extent_node_t* node = huge.Search(&key);
MOZ_ASSERT(node);
MOZ_ASSERT(node->mSize == aOldSize);
MOZ_RELEASE_ASSERT(node->mArena == this);
huge_allocated += psize - aOldSize;
huge_operations++;
// No need to change huge_mapped, because we didn't
// (un)map anything.
node->mSize = psize;
}
if (aSize > aOldSize) {
ApplyZeroOrJunk((void*)((uintptr_t)aPtr + aOldSize), aSize - aOldSize);
}
return aPtr;
}
// If we get here, then aSize and aOldSize are different enough that we
// need to use a different size class. In that case, fall back to allocating
// new space and copying. Allow non-private arenas to switch arenas.
ret = (mIsPrivate ? this : choose_arena(aSize))->MallocHuge(aSize, false);
if (!ret) {
return nullptr;
}
copysize = (aSize < aOldSize) ? aSize : aOldSize;
#ifdef VM_COPY_MIN
if (copysize >= VM_COPY_MIN) {
pages_copy(ret, aPtr, copysize);
} else
#endif
{
memcpy(ret, aPtr, copysize);
}
idalloc(aPtr, this);
return ret;
}
static void huge_dalloc(void* aPtr, arena_t* aArena) {
extent_node_t* node;
size_t mapped = 0;
{
extent_node_t key;
MutexAutoLock lock(huge_mtx);
// Extract from tree of huge allocations.
key.mAddr = aPtr;
node = huge.Search(&key);
MOZ_RELEASE_ASSERT(node, "Double-free?");
MOZ_ASSERT(node->mAddr == aPtr);
MOZ_RELEASE_ASSERT(!aArena || node->mArena == aArena);
// See AllocInfo::Arena.
MOZ_RELEASE_ASSERT(node->mArenaId == node->mArena->mId);
huge.Remove(node);
mapped = CHUNK_CEILING(node->mSize + gPageSize);
huge_allocated -= node->mSize;
huge_mapped -= mapped;
huge_operations++;
}
// Unmap chunk.
chunk_dealloc(node->mAddr, mapped, HUGE_CHUNK);
ExtentAlloc::dealloc(node);
}
size_t GetKernelPageSize() {
static size_t kernel_page_size = ([]() {
#ifdef XP_WIN
SYSTEM_INFO info;
GetSystemInfo(&info);
return info.dwPageSize;
#else
long result = sysconf(_SC_PAGESIZE);
MOZ_ASSERT(result != -1);
return result;
#endif
})();
return kernel_page_size;
}
// Returns whether the allocator was successfully initialized.
static bool malloc_init_hard() {
unsigned i;
const char* opts;
AutoLock<StaticMutex> lock(gInitLock);
if (malloc_initialized) {
// Another thread initialized the allocator before this one
// acquired gInitLock.
return true;
}
if (!thread_arena.init()) {
return true;
}
// Get page size and number of CPUs
const size_t page_size = GetKernelPageSize();
// We assume that the page size is a power of 2.
MOZ_ASSERT(IsPowerOfTwo(page_size));
#ifdef MALLOC_STATIC_PAGESIZE
if (gPageSize % page_size) {
_malloc_message(
_getprogname(),
"Compile-time page size does not divide the runtime one.\n");
MOZ_CRASH();
}
#else
gRealPageSize = gPageSize = page_size;
#endif
// Get runtime configuration.
if ((opts = getenv("MALLOC_OPTIONS"))) {
for (i = 0; opts[i] != '\0'; i++) {
// All options are single letters, some take a *prefix* numeric argument.
// Parse the argument.
unsigned prefix_arg = 0;
while (opts[i] >= '0' && opts[i] <= '9') {
prefix_arg *= 10;
prefix_arg += opts[i] - '0';
i++;
}
switch (opts[i]) {
case 'f':
opt_dirty_max >>= prefix_arg ? prefix_arg : 1;
break;
case 'F':
prefix_arg = prefix_arg ? prefix_arg : 1;
if (opt_dirty_max == 0) {
opt_dirty_max = 1;
prefix_arg--;
}
opt_dirty_max <<= prefix_arg;
if (opt_dirty_max == 0) {
// If the shift above overflowed all the bits then clamp the result
// instead. If we started with DIRTY_MAX_DEFAULT then this will
// always be a power of two so choose the maximum power of two that
// fits in a size_t.
opt_dirty_max = size_t(1) << (sizeof(size_t) * CHAR_BIT - 1);
}
break;
#ifdef MALLOC_RUNTIME_CONFIG
case 'j':
opt_junk = false;
break;
case 'J':
opt_junk = true;
break;
case 'q':
// The argument selects how much poisoning to do.
opt_poison = NONE;
break;
case 'Q':
if (opts[i + 1] == 'Q') {
// Maximum poisoning.
i++;
opt_poison = ALL;
} else {
opt_poison = SOME;
opt_poison_size = kCacheLineSize * prefix_arg;
}
break;
case 'z':
opt_zero = false;
break;
case 'Z':
opt_zero = true;
break;
# ifndef MALLOC_STATIC_PAGESIZE
case 'P':
MOZ_ASSERT(gPageSize >= 4_KiB);
MOZ_ASSERT(gPageSize <= 64_KiB);
prefix_arg = prefix_arg ? prefix_arg : 1;
gPageSize <<= prefix_arg;
// We know that if the shift causes gPageSize to be zero then it's
// because it shifted all the bits off. We didn't start with zero.
// Therefore if gPageSize is out of bounds we set it to 64KiB.
if (gPageSize < 4_KiB || gPageSize > 64_KiB) {
gPageSize = 64_KiB;
}
break;
# endif
#endif
case 'r':
opt_randomize_small = false;
break;
case 'R':
opt_randomize_small = true;
break;
default: {
char cbuf[2];
cbuf[0] = opts[i];
cbuf[1] = '\0';
_malloc_message(_getprogname(),
": (malloc) Unsupported character "
"in malloc options: '",
cbuf, "'\n");
}
}
}
}
#ifndef MALLOC_STATIC_PAGESIZE
DefineGlobals();
#endif
gRecycledSize = 0;
chunks_init();
huge_init();
base_init();
// Initialize arenas collection here.
if (!gArenas.Init()) {
return false;
}
// Assign the default arena to the initial thread.
thread_arena.set(gArenas.GetDefault());
if (!gChunkRTree.Init()) {
return false;
}
malloc_initialized = true;
// Dummy call so that the function is not removed by dead-code elimination
Debug::jemalloc_ptr_info(nullptr);
#if !defined(XP_WIN) && !defined(XP_DARWIN)
// Prevent potential deadlock on malloc locks after fork.
pthread_atfork(_malloc_prefork, _malloc_postfork_parent,
_malloc_postfork_child);
#endif
return true;
}
// End general internal functions.
// ***************************************************************************
// Begin malloc(3)-compatible functions.
// The BaseAllocator class is a helper class that implements the base allocator
// functions (malloc, calloc, realloc, free, memalign) for a given arena,
// or an appropriately chosen arena (per choose_arena()) when none is given.
struct BaseAllocator {
#define MALLOC_DECL(name, return_type, ...) \
inline return_type name(__VA_ARGS__);
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
#include "malloc_decls.h"
explicit BaseAllocator(arena_t* aArena) : mArena(aArena) {}
private:
arena_t* mArena;
};
#define MALLOC_DECL(name, return_type, ...) \
inline return_type MozJemalloc::name( \
ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) { \
BaseAllocator allocator(nullptr); \
return allocator.name(ARGS_HELPER(ARGS, ##__VA_ARGS__)); \
}
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
#include "malloc_decls.h"
inline void* BaseAllocator::malloc(size_t aSize) {
void* ret;
arena_t* arena;
if (!malloc_init()) {
ret = nullptr;
goto RETURN;
}
if (aSize == 0) {
aSize = 1;
}
// If mArena is non-null, it must not be in the first page.
MOZ_DIAGNOSTIC_ASSERT_IF(mArena, (size_t)mArena >= gPageSize);
arena = mArena ? mArena : choose_arena(aSize);
ret = arena->Malloc(aSize, /* aZero = */ false);
RETURN:
if (!ret) {
errno = ENOMEM;
}
return ret;
}
inline void* BaseAllocator::memalign(size_t aAlignment, size_t aSize) {
MOZ_ASSERT(((aAlignment - 1) & aAlignment) == 0);
if (!malloc_init()) {
return nullptr;
}
if (aSize == 0) {
aSize = 1;
}
aAlignment = aAlignment < sizeof(void*) ? sizeof(void*) : aAlignment;
arena_t* arena = mArena ? mArena : choose_arena(aSize);
return arena->Palloc(aAlignment, aSize);
}
inline void* BaseAllocator::calloc(size_t aNum, size_t aSize) {
void* ret;
if (malloc_init()) {
CheckedInt<size_t> checkedSize = CheckedInt<size_t>(aNum) * aSize;
if (checkedSize.isValid()) {
size_t allocSize = checkedSize.value();
if (allocSize == 0) {
allocSize = 1;
}
arena_t* arena = mArena ? mArena : choose_arena(allocSize);
ret = arena->Malloc(allocSize, /* aZero = */ true);
} else {
ret = nullptr;
}
} else {
ret = nullptr;
}
if (!ret) {
errno = ENOMEM;
}
return ret;
}
inline void* BaseAllocator::realloc(void* aPtr, size_t aSize) {
void* ret;
if (aSize == 0) {
aSize = 1;
}
if (aPtr) {
MOZ_RELEASE_ASSERT(malloc_initialized);
auto info = AllocInfo::Get(aPtr);
auto arena = info.Arena();
MOZ_RELEASE_ASSERT(!mArena || arena == mArena);
ret = arena->Ralloc(aPtr, aSize, info.Size());
} else {
if (!malloc_init()) {
ret = nullptr;
} else {
arena_t* arena = mArena ? mArena : choose_arena(aSize);
ret = arena->Malloc(aSize, /* aZero = */ false);
}
}
if (!ret) {
errno = ENOMEM;
}
return ret;
}
inline void BaseAllocator::free(void* aPtr) {
size_t offset;
// A version of idalloc that checks for nullptr pointer.
offset = GetChunkOffsetForPtr(aPtr);
if (offset != 0) {
MOZ_RELEASE_ASSERT(malloc_initialized);
arena_dalloc(aPtr, offset, mArena);
} else if (aPtr) {
MOZ_RELEASE_ASSERT(malloc_initialized);
huge_dalloc(aPtr, mArena);
}
}
inline int MozJemalloc::posix_memalign(void** aMemPtr, size_t aAlignment,
size_t aSize) {
return AlignedAllocator<memalign>::posix_memalign(aMemPtr, aAlignment, aSize);
}
inline void* MozJemalloc::aligned_alloc(size_t aAlignment, size_t aSize) {
return AlignedAllocator<memalign>::aligned_alloc(aAlignment, aSize);
}
inline void* MozJemalloc::valloc(size_t aSize) {
return AlignedAllocator<memalign>::valloc(aSize);
}
// End malloc(3)-compatible functions.
// ***************************************************************************
// Begin non-standard functions.
// This was added by Mozilla for use by SQLite.
inline size_t MozJemalloc::malloc_good_size(size_t aSize) {
if (aSize <= gMaxLargeClass) {
// Small or large
aSize = SizeClass(aSize).Size();
} else {
// Huge. We use PAGE_CEILING to get psize, instead of using
// CHUNK_CEILING to get csize. This ensures that this
// malloc_usable_size(malloc(n)) always matches
// malloc_good_size(n).
aSize = PAGE_CEILING(aSize);
}
return aSize;
}
inline size_t MozJemalloc::malloc_usable_size(usable_ptr_t aPtr) {
return AllocInfo::GetValidated(aPtr).Size();
}
inline void MozJemalloc::jemalloc_stats_internal(
jemalloc_stats_t* aStats, jemalloc_bin_stats_t* aBinStats) {
size_t non_arena_mapped, chunk_header_size;
if (!aStats) {
return;
}
if (!malloc_init()) {
memset(aStats, 0, sizeof(*aStats));
return;
}
if (aBinStats) {
memset(aBinStats, 0, sizeof(jemalloc_bin_stats_t) * NUM_SMALL_CLASSES);
}
// Gather runtime settings.
aStats->opt_junk = opt_junk;
aStats->opt_randomize_small = opt_randomize_small;
aStats->opt_zero = opt_zero;
aStats->quantum = kQuantum;
aStats->quantum_max = kMaxQuantumClass;
aStats->quantum_wide = kQuantumWide;
aStats->quantum_wide_max = kMaxQuantumWideClass;
aStats->subpage_max = gMaxSubPageClass;
aStats->large_max = gMaxLargeClass;
aStats->chunksize = kChunkSize;
aStats->page_size = gPageSize;
aStats->dirty_max = opt_dirty_max;
// Gather current memory usage statistics.
aStats->narenas = 0;
aStats->mapped = 0;
aStats->allocated = 0;
aStats->waste = 0;
aStats->pages_dirty = 0;
aStats->pages_fresh = 0;
aStats->pages_madvised = 0;
aStats->bookkeeping = 0;
aStats->bin_unused = 0;
non_arena_mapped = 0;
// Get huge mapped/allocated.
{
MutexAutoLock lock(huge_mtx);
non_arena_mapped += huge_mapped;
aStats->allocated += huge_allocated;
aStats->num_operations += huge_operations;
MOZ_ASSERT(huge_mapped >= huge_allocated);
}
// Get base mapped/allocated.
{
MutexAutoLock lock(base_mtx);
non_arena_mapped += base_mapped;
aStats->bookkeeping += base_committed;
MOZ_ASSERT(base_mapped >= base_committed);
}
gArenas.mLock.Lock();
// Stats can only read complete information if its run on the main thread.
MOZ_ASSERT(gArenas.IsOnMainThreadWeak());
// Iterate over arenas.
for (auto arena : gArenas.iter()) {
// Cannot safely read stats for this arena and therefore stats would be
// incomplete.
MOZ_ASSERT(arena->mLock.SafeOnThisThread());
size_t arena_mapped, arena_allocated, arena_committed, arena_dirty,
arena_fresh, arena_madvised, j, arena_unused, arena_headers;
arena_headers = 0;
arena_unused = 0;
{
MaybeMutexAutoLock lock(arena->mLock);
arena_mapped = arena->mStats.mapped;
// "committed" counts dirty and allocated memory.
arena_committed = arena->mStats.committed << gPageSize2Pow;
arena_allocated =
arena->mStats.allocated_small + arena->mStats.allocated_large;
arena_dirty = arena->mNumDirty << gPageSize2Pow;
arena_fresh = arena->mNumFresh << gPageSize2Pow;
arena_madvised = arena->mNumMAdvised << gPageSize2Pow;
aStats->num_operations += arena->mStats.operations;
for (j = 0; j < NUM_SMALL_CLASSES; j++) {
arena_bin_t* bin = &arena->mBins[j];
size_t bin_unused = 0;
size_t num_non_full_runs = 0;
for (arena_run_t& run : bin->mNonFullRuns) {
MOZ_DIAGNOSTIC_ASSERT(run.mMagic == ARENA_RUN_MAGIC);
MOZ_RELEASE_ASSERT(run.mNumFree > 0 &&
run.mNumFree < bin->mRunNumRegions);
MOZ_RELEASE_ASSERT(run.mBin == bin);
MOZ_RELEASE_ASSERT(bin->mNonFullRuns.ElementIsLinkedWell(&run));
arena_chunk_t* chunk = GetChunkForPtr(&run);
MOZ_RELEASE_ASSERT(chunk->arena == arena);
bin_unused += run.mNumFree * bin->mSizeClass;
num_non_full_runs++;
}
arena_unused += bin_unused;
arena_headers += bin->mNumRuns * bin->mRunFirstRegionOffset;
if (aBinStats) {
aBinStats[j].size = bin->mSizeClass;
aBinStats[j].num_non_full_runs += num_non_full_runs;
aBinStats[j].num_runs += bin->mNumRuns;
aBinStats[j].bytes_unused += bin_unused;
size_t bytes_per_run = static_cast<size_t>(bin->mRunSizePages)
<< gPageSize2Pow;
aBinStats[j].bytes_total +=
bin->mNumRuns * (bytes_per_run - bin->mRunFirstRegionOffset);
aBinStats[j].bytes_per_run = bytes_per_run;
aBinStats[j].regions_per_run = bin->mRunNumRegions;
}
}
}
MOZ_ASSERT(arena_mapped >= arena_committed);
MOZ_ASSERT(arena_committed >= arena_allocated + arena_dirty);
aStats->mapped += arena_mapped;
aStats->allocated += arena_allocated;
aStats->pages_dirty += arena_dirty;
aStats->pages_fresh += arena_fresh;
aStats->pages_madvised += arena_madvised;
// "waste" is committed memory that is neither dirty nor
// allocated. If you change this definition please update
// memory/replace/logalloc/replay/Replay.cpp's jemalloc_stats calculation of
// committed.
MOZ_ASSERT(arena_committed >=
(arena_allocated + arena_dirty + arena_unused + arena_headers));
aStats->waste += arena_committed - arena_allocated - arena_dirty -
arena_unused - arena_headers;
aStats->bin_unused += arena_unused;
aStats->bookkeeping += arena_headers;
aStats->narenas++;
}
gArenas.mLock.Unlock();
// Account for arena chunk headers in bookkeeping rather than waste.
chunk_header_size =
((aStats->mapped / aStats->chunksize) * (gChunkHeaderNumPages - 1))
<< gPageSize2Pow;
aStats->mapped += non_arena_mapped;
aStats->bookkeeping += chunk_header_size;
aStats->waste -= chunk_header_size;
MOZ_ASSERT(aStats->mapped >= aStats->allocated + aStats->waste +
aStats->pages_dirty + aStats->bookkeeping);
}
inline void MozJemalloc::jemalloc_stats_lite(jemalloc_stats_lite_t* aStats) {
if (!aStats) {
return;
}
if (!malloc_init()) {
memset(aStats, 0, sizeof(*aStats));
return;
}
aStats->allocated_bytes = 0;
aStats->num_operations = 0;
// Get huge mapped/allocated.
{
MutexAutoLock lock(huge_mtx);
aStats->allocated_bytes += huge_allocated;
aStats->num_operations += huge_operations;
MOZ_ASSERT(huge_mapped >= huge_allocated);
}
{
MutexAutoLock lock(gArenas.mLock);
for (auto arena : gArenas.iter()) {
// We don't need to lock the arena to access these fields.
aStats->allocated_bytes += arena->AllocatedBytes();
aStats->num_operations += arena->Operations();
}
aStats->num_operations += gArenas.OperationsDisposedArenas();
}
}
inline size_t MozJemalloc::jemalloc_stats_num_bins() {
return NUM_SMALL_CLASSES;
}
inline void MozJemalloc::jemalloc_set_main_thread() {
MOZ_ASSERT(malloc_initialized);
gArenas.SetMainThread();
}
#ifdef MALLOC_DOUBLE_PURGE
// Explicitly remove all of this chunk's MADV_FREE'd pages from memory.
static size_t hard_purge_chunk(arena_chunk_t* aChunk) {
size_t total_npages = 0;
// See similar logic in arena_t::Purge().
for (size_t i = gChunkHeaderNumPages; i < gChunkNumPages; i++) {
// Find all adjacent pages with CHUNK_MAP_MADVISED set.
size_t npages;
for (npages = 0; aChunk->map[i + npages].bits & CHUNK_MAP_MADVISED &&
i + npages < gChunkNumPages;
npages++) {
// Turn off the page's CHUNK_MAP_MADVISED bit and turn on its
// CHUNK_MAP_FRESH bit.
MOZ_DIAGNOSTIC_ASSERT(!(aChunk->map[i + npages].bits &
(CHUNK_MAP_FRESH | CHUNK_MAP_DECOMMITTED)));
aChunk->map[i + npages].bits ^= (CHUNK_MAP_MADVISED | CHUNK_MAP_FRESH);
}
// We could use mincore to find out which pages are actually
// present, but it's not clear that's better.
if (npages > 0) {
pages_decommit(((char*)aChunk) + (i << gPageSize2Pow),
npages << gPageSize2Pow);
Unused << pages_commit(((char*)aChunk) + (i << gPageSize2Pow),
npages << gPageSize2Pow);
}
total_npages += npages;
i += npages;
}
return total_npages;
}
// Explicitly remove all of this arena's MADV_FREE'd pages from memory.
void arena_t::HardPurge() {
MaybeMutexAutoLock lock(mLock);
while (!mChunksMAdvised.isEmpty()) {
arena_chunk_t* chunk = mChunksMAdvised.popFront();
size_t npages = hard_purge_chunk(chunk);
mNumMAdvised -= npages;
mNumFresh += npages;
}
}
inline void MozJemalloc::jemalloc_purge_freed_pages() {
if (malloc_initialized) {
MutexAutoLock lock(gArenas.mLock);
MOZ_ASSERT(gArenas.IsOnMainThreadWeak());
for (auto arena : gArenas.iter()) {
arena->HardPurge();
}
}
}
#else // !defined MALLOC_DOUBLE_PURGE
inline void MozJemalloc::jemalloc_purge_freed_pages() {
// Do nothing.
}
#endif // defined MALLOC_DOUBLE_PURGE
inline void MozJemalloc::jemalloc_free_dirty_pages(void) {
if (malloc_initialized) {
gArenas.MayPurgeAll(PurgeUnconditional);
}
}
inline void MozJemalloc::jemalloc_free_excess_dirty_pages(void) {
if (malloc_initialized) {
gArenas.MayPurgeAll(PurgeIfThreshold);
}
}
#ifndef NON_RANDOM_ARENA_IDS
inline arena_t* ArenaCollection::GetByIdInternal(Tree& aTree,
arena_id_t aArenaId) {
// Use AlignedStorage2 to avoid running the arena_t constructor, while
// we only need it as a placeholder for mId.
mozilla::AlignedStorage2<arena_t> key;
key.addr()->mId = aArenaId;
return aTree.Search(key.addr());
}
#endif
inline arena_t* ArenaCollection::GetById(arena_id_t aArenaId, bool aIsPrivate) {
if (!malloc_initialized) {
return nullptr;
}
#ifdef NON_RANDOM_ARENA_IDS
// This function is never called with aIsPrivate = false, let's make sure it
// doesn't silently change while we're making that assumption below because
// we can't resolve non-private arenas this way.
MOZ_RELEASE_ASSERT(aIsPrivate);
// This function is not expected to be called before at least one private
// arena was created.
// coverity[missing_lock]
MOZ_RELEASE_ASSERT(mArenaIdKey);
arena_id_t id = (aArenaId << mArenaIdRotation) |
(aArenaId >> (sizeof(void*) * 8 - mArenaIdRotation));
arena_t* result = reinterpret_cast<arena_t*>(id ^ mArenaIdKey);
#else
Tree* tree = nullptr;
if (aIsPrivate) {
if (ArenaIdIsMainThreadOnly(aArenaId)) {
// The main thread only arenas support lock free access, so it's desirable
// to do GetById without taking mLock either.
//
// Races can occur between writers and writers, or between writers and
// readers. The only writer is the main thread and it will never race
// against itself so we can elude the lock when the main thread is
// reading.
MOZ_ASSERT(IsOnMainThread());
MOZ_PUSH_IGNORE_THREAD_SAFETY
arena_t* result = GetByIdInternal(mMainThreadArenas, aArenaId);
MOZ_POP_THREAD_SAFETY
MOZ_RELEASE_ASSERT(result);
return result;
}
tree = &mPrivateArenas;
} else {
tree = &mArenas;
}
MutexAutoLock lock(mLock);
arena_t* result = GetByIdInternal(*tree, aArenaId);
#endif
MOZ_RELEASE_ASSERT(result);
MOZ_RELEASE_ASSERT(result->mId == aArenaId);
return result;
}
inline arena_id_t MozJemalloc::moz_create_arena_with_params(
arena_params_t* aParams) {
if (malloc_init()) {
arena_t* arena = gArenas.CreateArena(/* IsPrivate = */ true, aParams);
return arena->mId;
}
return 0;
}
inline void MozJemalloc::moz_dispose_arena(arena_id_t aArenaId) {
arena_t* arena = gArenas.GetById(aArenaId, /* IsPrivate = */ true);
MOZ_RELEASE_ASSERT(arena);
gArenas.DisposeArena(arena);
}
inline void MozJemalloc::moz_set_max_dirty_page_modifier(int32_t aModifier) {
if (malloc_init()) {
gArenas.SetDefaultMaxDirtyPageModifier(aModifier);
}
}
inline void MozJemalloc::jemalloc_reset_small_alloc_randomization(
bool aRandomizeSmall) {
// When this process got forked by ForkServer then it inherited the existing
// state of mozjemalloc. Specifically, parsing of MALLOC_OPTIONS has already
// been done but it may not reflect anymore the current set of options after
// the fork().
//
// Similar behavior is also present on Android where it is also required to
// perform this step.
//
// Content process will have randomization on small malloc disabled via the
// MALLOC_OPTIONS environment variable set by parent process, missing this
// will lead to serious performance regressions because CPU prefetch will
// break, cf bug 1912262. However on forkserver-forked Content processes, the
// environment is not yet reset when the postfork child handler is being
// called.
//
// This API is here to allow those Content processes (spawned by ForkServer or
// Android service) to notify jemalloc to turn off the randomization on small
// allocations and perform the required reinitialization of already existing
// arena's PRNG. It is important to make sure that the PRNG state is properly
// re-initialized otherwise child processes would share all the same state.
{
AutoLock<StaticMutex> lock(gInitLock);
opt_randomize_small = aRandomizeSmall;
}
MutexAutoLock lock(gArenas.mLock);
for (auto* arena : gArenas.iter()) {
// We can only initialize the PRNG for main-thread-only arenas from the main
// thread.
if (!arena->IsMainThreadOnly() || gArenas.IsOnMainThreadWeak()) {
arena->ResetSmallAllocRandomization();
}
}
}
inline bool MozJemalloc::moz_enable_deferred_purge(bool aEnabled) {
return gArenas.SetDeferredPurge(aEnabled);
}
inline purge_result_t MozJemalloc::moz_may_purge_now(
bool aPeekOnly, uint32_t aReuseGraceMS,
const Maybe<std::function<bool()>>& aKeepGoing) {
return gArenas.MayPurgeSteps(aPeekOnly, aReuseGraceMS, aKeepGoing);
}
inline void ArenaCollection::AddToOutstandingPurges(arena_t* aArena) {
MOZ_ASSERT(aArena);
// We cannot trust the caller to know whether the element was already added
// from another thread given we have our own lock.
MutexAutoLock lock(mPurgeListLock);
if (!mOutstandingPurges.ElementProbablyInList(aArena)) {
mOutstandingPurges.pushBack(aArena);
}
}
inline bool ArenaCollection::RemoveFromOutstandingPurges(arena_t* aArena) {
MOZ_ASSERT(aArena);
// We cannot trust the caller to know whether the element was already removed
// from another thread given we have our own lock.
MutexAutoLock lock(mPurgeListLock);
if (mOutstandingPurges.ElementProbablyInList(aArena)) {
mOutstandingPurges.remove(aArena);
return true;
}
return false;
}
purge_result_t ArenaCollection::MayPurgeSteps(
bool aPeekOnly, uint32_t aReuseGraceMS,
const Maybe<std::function<bool()>>& aKeepGoing) {
// This only works on the main thread because it may process main-thread-only
// arenas.
MOZ_ASSERT(IsOnMainThreadWeak());
uint64_t now = GetTimestampNS();
uint64_t reuseGraceNS = (uint64_t)aReuseGraceMS * 1000 * 1000;
arena_t* found = nullptr;
{
MutexAutoLock lock(mPurgeListLock);
if (mOutstandingPurges.isEmpty()) {
return purge_result_t::Done;
}
for (arena_t& arena : mOutstandingPurges) {
if (now - arena.mLastSignificantReuseNS >= reuseGraceNS) {
found = &arena;
break;
}
}
if (!found) {
return purge_result_t::WantsLater;
}
if (aPeekOnly) {
return purge_result_t::NeedsMore;
}
// We need to avoid the invalid state where mIsDeferredPurgePending is set
// but the arena is not in the list or about to be added. So remove the
// arena from the list before calling Purge().
mOutstandingPurges.remove(found);
}
arena_t::PurgeResult pr;
do {
pr = found->Purge(PurgeIfThreshold);
now = GetTimestampNS();
} while (pr == arena_t::PurgeResult::Continue &&
(now - found->mLastSignificantReuseNS >= reuseGraceNS) &&
aKeepGoing && (*aKeepGoing)());
if (pr == arena_t::PurgeResult::Continue) {
// If there's more work to do we re-insert the arena into the purge queue.
// If the arena was busy we don't since the other thread that's purging it
// will finish that work.
// Note that after the above Purge() and taking the lock below there's a
// chance another thread may be purging the arena and clear
// mIsDeferredPurgePending. Resulting in the state of being in the list
// with that flag clear. That's okay since the next time a purge occurs
// (and one will because it's in the list) it'll clear the flag and the
// state will be consistent again.
MutexAutoLock lock(mPurgeListLock);
if (!mOutstandingPurges.ElementProbablyInList(found)) {
// Given we want to continue to purge this arena, push it to the front
// to increase the probability to find it fast.
mOutstandingPurges.pushFront(found);
}
} else if (pr == arena_t::PurgeResult::Dying) {
delete found;
}
// Even if there is no other arena that needs work, let the caller just call
// us again and we will do the above checks then and return their result.
// Note that in the current surrounding setting this may (rarely) cause a
// new slice of our idle task runner if we are exceeding idle budget.
return purge_result_t::NeedsMore;
}
void ArenaCollection::MayPurgeAll(PurgeCondition aCond) {
MutexAutoLock lock(mLock);
for (auto* arena : iter()) {
// Arenas that are not IsMainThreadOnly can be purged from any thread.
// So we do what we can even if called from another thread.
if (!arena->IsMainThreadOnly() || IsOnMainThreadWeak()) {
RemoveFromOutstandingPurges(arena);
arena_t::PurgeResult pr;
do {
pr = arena->Purge(aCond);
} while (pr == arena_t::PurgeResult::Continue);
// No arena can die here because we're holding the arena collection lock.
// Arenas are removed from the collection before setting their mDying
// flag.
MOZ_RELEASE_ASSERT(pr != arena_t::PurgeResult::Dying);
}
}
}
#define MALLOC_DECL(name, return_type, ...) \
inline return_type MozJemalloc::moz_arena_##name( \
arena_id_t aArenaId, ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) { \
BaseAllocator allocator( \
gArenas.GetById(aArenaId, /* IsPrivate = */ true)); \
return allocator.name(ARGS_HELPER(ARGS, ##__VA_ARGS__)); \
}
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
#include "malloc_decls.h"
// End non-standard functions.
// ***************************************************************************
#ifndef XP_WIN
// Begin library-private functions, used by threading libraries for protection
// of malloc during fork(). These functions are only called if the program is
// running in threaded mode, so there is no need to check whether the program
// is threaded here.
//
// Note that the only way to keep the main-thread-only arenas in a consistent
// state for the child is if fork is called from the main thread only. Or the
// child must not use them, eg it should call exec(). We attempt to prevent the
// child for accessing these arenas by refusing to re-initialise them.
//
// This is only accessed in the fork handlers while gArenas.mLock is held.
static pthread_t gForkingThread;
# ifdef XP_DARWIN
// This is only accessed in the fork handlers while gArenas.mLock is held.
static pid_t gForkingProcess;
# endif
FORK_HOOK
void _malloc_prefork(void) MOZ_NO_THREAD_SAFETY_ANALYSIS {
// Acquire all mutexes in a safe order.
gArenas.mLock.Lock();
gForkingThread = pthread_self();
# ifdef XP_DARWIN
gForkingProcess = getpid();
# endif
for (auto arena : gArenas.iter()) {
if (arena->mLock.LockIsEnabled()) {
arena->mLock.Lock();
}
}
gArenas.mPurgeListLock.Lock();
base_mtx.Lock();
huge_mtx.Lock();
}
FORK_HOOK
void _malloc_postfork_parent(void) MOZ_NO_THREAD_SAFETY_ANALYSIS {
// Release all mutexes, now that fork() has completed.
huge_mtx.Unlock();
base_mtx.Unlock();
gArenas.mPurgeListLock.Unlock();
for (auto arena : gArenas.iter()) {
if (arena->mLock.LockIsEnabled()) {
arena->mLock.Unlock();
}
}
gArenas.mLock.Unlock();
}
FORK_HOOK
void _malloc_postfork_child(void) {
// Do this before iterating over the arenas.
gArenas.ResetMainThread();
// Reinitialize all mutexes, now that fork() has completed.
huge_mtx.Init();
base_mtx.Init();
gArenas.mPurgeListLock.Init();
MOZ_PUSH_IGNORE_THREAD_SAFETY
for (auto arena : gArenas.iter()) {
arena->mLock.Reinit(gForkingThread);
}
MOZ_POP_THREAD_SAFETY
gArenas.mLock.Init();
}
# ifdef XP_DARWIN
FORK_HOOK
void _malloc_postfork(void) {
// On MacOS we need to check if this is running in the parent or child
// process.
bool is_in_parent = getpid() == gForkingProcess;
gForkingProcess = 0;
if (is_in_parent) {
_malloc_postfork_parent();
} else {
_malloc_postfork_child();
}
}
# endif // XP_DARWIN
#endif // ! XP_WIN
// End library-private functions.
// ***************************************************************************
#ifdef MOZ_REPLACE_MALLOC
// Windows doesn't come with weak imports as they are possible with
// LD_PRELOAD or DYLD_INSERT_LIBRARIES on Linux/OSX. On this platform,
// the replacement functions are defined as variable pointers to the
// function resolved with GetProcAddress() instead of weak definitions
// of functions. On Android, the same needs to happen as well, because
// the Android linker doesn't handle weak linking with non LD_PRELOADed
// libraries, but LD_PRELOADing is not very convenient on Android, with
// the zygote.
# ifdef XP_DARWIN
# define MOZ_REPLACE_WEAK __attribute__((weak_import))
# elif defined(XP_WIN) || defined(ANDROID)
# define MOZ_DYNAMIC_REPLACE_INIT
# define replace_init replace_init_decl
# elif defined(__GNUC__)
# define MOZ_REPLACE_WEAK __attribute__((weak))
# endif
# include "replace_malloc.h"
# define MALLOC_DECL(name, return_type, ...) CanonicalMalloc::name,
// The default malloc table, i.e. plain allocations. It never changes. It's
// used by init(), and not used after that.
static const malloc_table_t gDefaultMallocTable = {
# include "malloc_decls.h"
};
// The malloc table installed by init(). It never changes from that point
// onward. It will be the same as gDefaultMallocTable if no replace-malloc tool
// is enabled at startup.
static malloc_table_t gOriginalMallocTable = {
# include "malloc_decls.h"
};
// The malloc table installed by jemalloc_replace_dynamic(). (Read the
// comments above that function for more details.)
static malloc_table_t gDynamicMallocTable = {
# include "malloc_decls.h"
};
// This briefly points to gDefaultMallocTable at startup. After that, it points
// to either gOriginalMallocTable or gDynamicMallocTable. It's atomic to avoid
// races when switching between tables.
static Atomic<malloc_table_t const*, mozilla::MemoryOrdering::Relaxed>
gMallocTablePtr;
# ifdef MOZ_DYNAMIC_REPLACE_INIT
# undef replace_init
typedef decltype(replace_init_decl) replace_init_impl_t;
static replace_init_impl_t* replace_init = nullptr;
# endif
# ifdef XP_WIN
typedef HMODULE replace_malloc_handle_t;
static replace_malloc_handle_t replace_malloc_handle() {
wchar_t replace_malloc_lib[1024];
if (GetEnvironmentVariableW(L"MOZ_REPLACE_MALLOC_LIB", replace_malloc_lib,
std::size(replace_malloc_lib)) > 0) {
return LoadLibraryW(replace_malloc_lib);
}
return nullptr;
}
# define REPLACE_MALLOC_GET_INIT_FUNC(handle) \
(replace_init_impl_t*)GetProcAddress(handle, "replace_init")
# elif defined(ANDROID)
# include <dlfcn.h>
typedef void* replace_malloc_handle_t;
static replace_malloc_handle_t replace_malloc_handle() {
const char* replace_malloc_lib = getenv("MOZ_REPLACE_MALLOC_LIB");
if (replace_malloc_lib && *replace_malloc_lib) {
return dlopen(replace_malloc_lib, RTLD_LAZY);
}
return nullptr;
}
# define REPLACE_MALLOC_GET_INIT_FUNC(handle) \
(replace_init_impl_t*)dlsym(handle, "replace_init")
# endif
static void replace_malloc_init_funcs(malloc_table_t*);
# ifdef MOZ_REPLACE_MALLOC_STATIC
extern "C" void logalloc_init(malloc_table_t*, ReplaceMallocBridge**);
extern "C" void dmd_init(malloc_table_t*, ReplaceMallocBridge**);
# endif
void phc_init(malloc_table_t*, ReplaceMallocBridge**);
bool Equals(const malloc_table_t& aTable1, const malloc_table_t& aTable2) {
return memcmp(&aTable1, &aTable2, sizeof(malloc_table_t)) == 0;
}
// Below is the malloc implementation overriding jemalloc and calling the
// replacement functions if they exist.
static ReplaceMallocBridge* gReplaceMallocBridge = nullptr;
static void init() {
malloc_table_t tempTable = gDefaultMallocTable;
# ifdef MOZ_DYNAMIC_REPLACE_INIT
replace_malloc_handle_t handle = replace_malloc_handle();
if (handle) {
replace_init = REPLACE_MALLOC_GET_INIT_FUNC(handle);
}
# endif
// Set this *before* calling replace_init, otherwise if replace_init calls
// malloc() we'll get an infinite loop.
gMallocTablePtr = &gDefaultMallocTable;
// Pass in the default allocator table so replace functions can copy and use
// it for their allocations. The replace_init() function should modify the
// table if it wants to be active, otherwise leave it unmodified.
if (replace_init) {
replace_init(&tempTable, &gReplaceMallocBridge);
}
# ifdef MOZ_REPLACE_MALLOC_STATIC
if (Equals(tempTable, gDefaultMallocTable)) {
logalloc_init(&tempTable, &gReplaceMallocBridge);
}
# ifdef MOZ_DMD
if (Equals(tempTable, gDefaultMallocTable)) {
dmd_init(&tempTable, &gReplaceMallocBridge);
}
# endif
# endif
if (!Equals(tempTable, gDefaultMallocTable)) {
replace_malloc_init_funcs(&tempTable);
}
gOriginalMallocTable = tempTable;
gMallocTablePtr = &gOriginalMallocTable;
}
// WARNING WARNING WARNING: this function should be used with extreme care. It
// is not as general-purpose as it looks. It is currently used by
// tools/profiler/core/memory_hooks.cpp for counting allocations and probably
// should not be used for any other purpose.
//
// This function allows the original malloc table to be temporarily replaced by
// a different malloc table. Or, if the argument is nullptr, it switches back to
// the original malloc table.
//
// Limitations:
//
// - It is not threadsafe. If multiple threads pass it the same
// `replace_init_func` at the same time, there will be data races writing to
// the malloc_table_t within that function.
//
// - Only one replacement can be installed. No nesting is allowed.
//
// - The new malloc table must be able to free allocations made by the original
// malloc table, and upon removal the original malloc table must be able to
// free allocations made by the new malloc table. This means the new malloc
// table can only do simple things like recording extra information, while
// delegating actual allocation/free operations to the original malloc table.
//
MOZ_JEMALLOC_API void jemalloc_replace_dynamic(
jemalloc_init_func replace_init_func) {
if (replace_init_func) {
malloc_table_t tempTable = gOriginalMallocTable;
(*replace_init_func)(&tempTable, &gReplaceMallocBridge);
if (!Equals(tempTable, gOriginalMallocTable)) {
replace_malloc_init_funcs(&tempTable);
// Temporarily switch back to the original malloc table. In the
// (supported) non-nested case, this is a no-op. But just in case this is
// a (unsupported) nested call, it makes the overwriting of
// gDynamicMallocTable less racy, because ongoing calls to malloc() and
// friends won't go through gDynamicMallocTable.
gMallocTablePtr = &gOriginalMallocTable;
gDynamicMallocTable = tempTable;
gMallocTablePtr = &gDynamicMallocTable;
// We assume that dynamic replaces don't occur close enough for a
// thread to still have old copies of the table pointer when the 2nd
// replace occurs.
}
} else {
// Switch back to the original malloc table.
gMallocTablePtr = &gOriginalMallocTable;
}
}
# define MALLOC_DECL(name, return_type, ...) \
inline return_type ReplaceMalloc::name( \
ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) { \
if (MOZ_UNLIKELY(!gMallocTablePtr)) { \
init(); \
} \
return (*gMallocTablePtr).name(ARGS_HELPER(ARGS, ##__VA_ARGS__)); \
}
# include "malloc_decls.h"
MOZ_JEMALLOC_API struct ReplaceMallocBridge* get_bridge(void) {
if (MOZ_UNLIKELY(!gMallocTablePtr)) {
init();
}
return gReplaceMallocBridge;
}
// posix_memalign, aligned_alloc, memalign and valloc all implement some kind
// of aligned memory allocation. For convenience, a replace-malloc library can
// skip defining replace_posix_memalign, replace_aligned_alloc and
// replace_valloc, and default implementations will be automatically derived
// from replace_memalign.
static void replace_malloc_init_funcs(malloc_table_t* table) {
if (table->posix_memalign == CanonicalMalloc::posix_memalign &&
table->memalign != CanonicalMalloc::memalign) {
table->posix_memalign =
AlignedAllocator<ReplaceMalloc::memalign>::posix_memalign;
}
if (table->aligned_alloc == CanonicalMalloc::aligned_alloc &&
table->memalign != CanonicalMalloc::memalign) {
table->aligned_alloc =
AlignedAllocator<ReplaceMalloc::memalign>::aligned_alloc;
}
if (table->valloc == CanonicalMalloc::valloc &&
table->memalign != CanonicalMalloc::memalign) {
table->valloc = AlignedAllocator<ReplaceMalloc::memalign>::valloc;
}
if (table->moz_create_arena_with_params ==
CanonicalMalloc::moz_create_arena_with_params &&
table->malloc != CanonicalMalloc::malloc) {
# define MALLOC_DECL(name, ...) \
table->name = DummyArenaAllocator<ReplaceMalloc>::name;
# define MALLOC_FUNCS MALLOC_FUNCS_ARENA_BASE
# include "malloc_decls.h"
}
if (table->moz_arena_malloc == CanonicalMalloc::moz_arena_malloc &&
table->malloc != CanonicalMalloc::malloc) {
# define MALLOC_DECL(name, ...) \
table->name = DummyArenaAllocator<ReplaceMalloc>::name;
# define MALLOC_FUNCS MALLOC_FUNCS_ARENA_ALLOC
# include "malloc_decls.h"
}
}
#endif // MOZ_REPLACE_MALLOC
// ***************************************************************************
// Definition of all the _impl functions
// GENERIC_MALLOC_DECL2_MINGW is only used for the MinGW build, and aliases
// the malloc funcs (e.g. malloc) to the je_ versions. It does not generate
// aliases for the other functions (jemalloc and arena functions).
//
// We do need aliases for the other mozglue.def-redirected functions though,
// these are done at the bottom of mozmemory_wrap.cpp
#define GENERIC_MALLOC_DECL2_MINGW(name, name_impl, return_type, ...) \
return_type name(ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) \
__attribute__((alias(MOZ_STRINGIFY(name_impl))));
#define GENERIC_MALLOC_DECL2(attributes, name, name_impl, return_type, ...) \
return_type name_impl(ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) attributes { \
return DefaultMalloc::name(ARGS_HELPER(ARGS, ##__VA_ARGS__)); \
}
#ifndef __MINGW32__
# define GENERIC_MALLOC_DECL(attributes, name, return_type, ...) \
GENERIC_MALLOC_DECL2(attributes, name, name##_impl, return_type, \
##__VA_ARGS__)
#else
# define GENERIC_MALLOC_DECL(attributes, name, return_type, ...) \
GENERIC_MALLOC_DECL2(attributes, name, name##_impl, return_type, \
##__VA_ARGS__) \
GENERIC_MALLOC_DECL2_MINGW(name, name##_impl, return_type, ##__VA_ARGS__)
#endif
#define NOTHROW_MALLOC_DECL(...) \
MOZ_MEMORY_API MACRO_CALL(GENERIC_MALLOC_DECL, (noexcept(true), __VA_ARGS__))
#define MALLOC_DECL(...) \
MOZ_MEMORY_API MACRO_CALL(GENERIC_MALLOC_DECL, (, __VA_ARGS__))
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC
#include "malloc_decls.h"
#undef GENERIC_MALLOC_DECL
#define GENERIC_MALLOC_DECL(attributes, name, return_type, ...) \
GENERIC_MALLOC_DECL2(attributes, name, name, return_type, ##__VA_ARGS__)
#define MALLOC_DECL(...) \
MOZ_JEMALLOC_API MACRO_CALL(GENERIC_MALLOC_DECL, (, __VA_ARGS__))
#define MALLOC_FUNCS (MALLOC_FUNCS_JEMALLOC | MALLOC_FUNCS_ARENA)
#include "malloc_decls.h"
// ***************************************************************************
#ifdef HAVE_DLFCN_H
# include <dlfcn.h>
#endif
#if defined(__GLIBC__) && !defined(__UCLIBC__)
// glibc provides the RTLD_DEEPBIND flag for dlopen which can make it possible
// to inconsistently reference libc's malloc(3)-compatible functions
// (bug 493541).
//
// These definitions interpose hooks in glibc. The functions are actually
// passed an extra argument for the caller return address, which will be
// ignored.
extern "C" {
MOZ_EXPORT void (*__free_hook)(void*) = free_impl;
MOZ_EXPORT void* (*__malloc_hook)(size_t) = malloc_impl;
MOZ_EXPORT void* (*__realloc_hook)(void*, size_t) = realloc_impl;
MOZ_EXPORT void* (*__memalign_hook)(size_t, size_t) = memalign_impl;
}
#elif defined(RTLD_DEEPBIND)
// XXX On systems that support RTLD_GROUP or DF_1_GROUP, do their
// implementations permit similar inconsistencies? Should STV_SINGLETON
// visibility be used for interposition where available?
# error \
"Interposing malloc is unsafe on this system without libc malloc hooks."
#endif
#ifdef XP_WIN
MOZ_EXPORT void* _recalloc(void* aPtr, size_t aCount, size_t aSize) {
size_t oldsize = aPtr ? AllocInfo::Get(aPtr).Size() : 0;
CheckedInt<size_t> checkedSize = CheckedInt<size_t>(aCount) * aSize;
if (!checkedSize.isValid()) {
return nullptr;
}
size_t newsize = checkedSize.value();
// In order for all trailing bytes to be zeroed, the caller needs to
// use calloc(), followed by recalloc(). However, the current calloc()
// implementation only zeros the bytes requested, so if recalloc() is
// to work 100% correctly, calloc() will need to change to zero
// trailing bytes.
aPtr = DefaultMalloc::realloc(aPtr, newsize);
if (aPtr && oldsize < newsize) {
memset((void*)((uintptr_t)aPtr + oldsize), 0, newsize - oldsize);
}
return aPtr;
}
// This impl of _expand doesn't ever actually expand or shrink blocks: it
// simply replies that you may continue using a shrunk block.
MOZ_EXPORT void* _expand(void* aPtr, size_t newsize) {
if (AllocInfo::Get(aPtr).Size() >= newsize) {
return aPtr;
}
return nullptr;
}
MOZ_EXPORT size_t _msize(void* aPtr) {
return DefaultMalloc::malloc_usable_size(aPtr);
}
#endif
#ifdef MOZ_PHC
// Compile PHC and mozjemalloc together so that PHC can inline mozjemalloc.
# include "PHC.cpp"
#endif
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