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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/. */
// Linux kernels since 5.17 have a feature for assigning names to
// ranges of anonymous memory (i.e., memory that doesn't have a "name"
// in the form of an underlying mapped file). These names are
// reported in /proc/<pid>/smaps alongside system-level memory usage
// information such as Proportional Set Size (memory usage adjusted
// for sharing between processes), which allows reporting this
// information at a finer granularity than would otherwise be possible
// (e.g., separating malloc() heap from JS heap).
//
// Existing memory can be tagged with MozTagAnonymousMemory(); it will
// tag the range of complete pages containing the given interval, so
// the results may be inexact if the range isn't page-aligned.
// MozTaggedAnonymousMmap() can be used like mmap() with an extra
// parameter, and will tag the returned memory if the mapping was
// successful (and if it was in fact anonymous).
//
// NOTE: The pointer given as the "tag" argument MUST remain valid as
// long as the mapping exists. The referenced string is read when
// /proc/<pid>/smaps or /proc/<pid>/maps is read, not when the tag is
// established, so freeing it or changing its contents will have
// unexpected results. Using a static string is probably best.
//
// Also note that this header can be used by both C and C++ code.
#ifndef mozilla_TaggedAnonymousMemory_h
#define mozilla_TaggedAnonymousMemory_h
#ifndef XP_WIN
# ifdef __wasi__
# include <stdlib.h>
# else
# include <sys/types.h>
# include <sys/mman.h>
# endif // __wasi__
# include "mozilla/Types.h"
# ifdef XP_LINUX
# ifdef __cplusplus
extern "C" {
# endif
MFBT_API void MozTagAnonymousMemory(const void* aPtr, size_t aLength,
const char* aTag);
MFBT_API void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt,
int aFlags, int aFd, off_t aOffset,
const char* aTag);
# ifdef __cplusplus
} // extern "C"
# endif
# else // XP_LINUX
static inline void MozTagAnonymousMemory(const void* aPtr, size_t aLength,
const char* aTag) {}
static inline void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength,
int aProt, int aFlags, int aFd,
off_t aOffset, const char* aTag) {
# ifdef __wasi__
MOZ_CRASH("We don't use this memory for WASI right now.");
return nullptr;
# else
return mmap(aAddr, aLength, aProt, aFlags, aFd, aOffset);
# endif
}
# endif // XP_LINUX
#endif // !XP_WIN
#endif // mozilla_TaggedAnonymousMemory_h
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