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Diffstat (limited to 'mozglue/baseprofiler/public/ProfileBufferChunk.h')
| -rw-r--r-- | mozglue/baseprofiler/public/ProfileBufferChunk.h | 543 |
1 files changed, 543 insertions, 0 deletions
diff --git a/mozglue/baseprofiler/public/ProfileBufferChunk.h b/mozglue/baseprofiler/public/ProfileBufferChunk.h new file mode 100644 index 0000000000..24a516bcaf --- /dev/null +++ b/mozglue/baseprofiler/public/ProfileBufferChunk.h @@ -0,0 +1,543 @@ +/* -*- Mode: C++; tab-width: 2; 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/. */ + +#ifndef ProfileBufferChunk_h +#define ProfileBufferChunk_h + +#include "mozilla/MemoryReporting.h" +#include "mozilla/ProfileBufferIndex.h" +#include "mozilla/Span.h" +#include "mozilla/TimeStamp.h" +#include "mozilla/UniquePtr.h" + +#if defined(MOZ_MEMORY) +# include "mozmemory.h" +#endif + +#include <algorithm> +#include <limits> +#include <type_traits> + +#ifdef DEBUG +# include <cstdio> +#endif + +namespace mozilla { + +// Represents a single chunk of memory, with a link to the next chunk (or null). +// +// A chunk is made of an internal header (which contains a public part) followed +// by user-accessible bytes. +// +// +---------------+---------+----------------------------------------------+ +// | public Header | private | memory containing user blocks | +// +---------------+---------+----------------------------------------------+ +// <---------------BufferBytes()------------------> +// <------------------------------ChunkBytes()------------------------------> +// +// The chunk can reserve "blocks", but doesn't know the internal contents of +// each block, it only knows where the first one starts, and where the last one +// ends (which is where the next one will begin, if not already out of range). +// It is up to the user to add structure to each block so that they can be +// distinguished when later read. +// +// +---------------+---------+----------------------------------------------+ +// | public Header | private | [1st block]...[last full block] | +// +---------------+---------+----------------------------------------------+ +// ChunkHeader().mOffsetFirstBlock ^ ^ +// ChunkHeader().mOffsetPastLastBlock --' +// +// It is possible to attempt to reserve more than the remaining space, in which +// case only what is available is returned. The caller is responsible for using +// another chunk, reserving a block "tail" in it, and using both parts to +// constitute a full block. (This initial tail may be empty in some chunks.) +// +// +---------------+---------+----------------------------------------------+ +// | public Header | private | tail][1st block]...[last full block][head... | +// +---------------+---------+----------------------------------------------+ +// ChunkHeader().mOffsetFirstBlock ^ ^ +// ChunkHeader().mOffsetPastLastBlock --' +// +// Each Chunk has an internal state (checked in DEBUG builds) that directs how +// to use it during creation, initialization, use, end of life, recycling, and +// destruction. See `State` below for details. +// In particular: +// - `ReserveInitialBlockAsTail()` must be called before the first `Reserve()` +// after construction or recycling, even with a size of 0 (no actual tail), +// - `MarkDone()` and `MarkRecycled()` must be called as appropriate. +class ProfileBufferChunk { + public: + using Byte = uint8_t; + using Length = uint32_t; + + using SpanOfBytes = Span<Byte>; + + // Hint about the size of the metadata (public and private headers). + // `Create()` below takes the minimum *buffer* size, so the minimum total + // Chunk size is at least `SizeofChunkMetadata() + aMinBufferBytes`. + [[nodiscard]] static constexpr Length SizeofChunkMetadata() { + return static_cast<Length>(sizeof(InternalHeader)); + } + + // Allocate space for a chunk with a given minimum size, and construct it. + // The actual size may be higher, to match the actual space taken in the + // memory pool. + [[nodiscard]] static UniquePtr<ProfileBufferChunk> Create( + Length aMinBufferBytes) { + // We need at least one byte, to cover the always-present `mBuffer` byte. + aMinBufferBytes = std::max(aMinBufferBytes, Length(1)); + // Trivial struct with the same alignment as `ProfileBufferChunk`, and size + // equal to that alignment, because typically the sizeof of an object is + // a multiple of its alignment. + struct alignas(alignof(InternalHeader)) ChunkStruct { + Byte c[alignof(InternalHeader)]; + }; + static_assert(std::is_trivial_v<ChunkStruct>, + "ChunkStruct must be trivial to avoid any construction"); + // Allocate an array of that struct, enough to contain the expected + // `ProfileBufferChunk` (with its header+buffer). + size_t count = (sizeof(InternalHeader) + aMinBufferBytes + + (alignof(InternalHeader) - 1)) / + alignof(InternalHeader); +#if defined(MOZ_MEMORY) + // Potentially expand the array to use more of the effective allocation. + count = (malloc_good_size(count * sizeof(ChunkStruct)) + + (sizeof(ChunkStruct) - 1)) / + sizeof(ChunkStruct); +#endif + auto chunkStorage = MakeUnique<ChunkStruct[]>(count); + MOZ_ASSERT(reinterpret_cast<uintptr_t>(chunkStorage.get()) % + alignof(InternalHeader) == + 0); + // After the allocation, compute the actual chunk size (including header). + const size_t chunkBytes = count * sizeof(ChunkStruct); + MOZ_ASSERT(chunkBytes >= sizeof(ProfileBufferChunk), + "Not enough space to construct a ProfileBufferChunk"); + MOZ_ASSERT(chunkBytes <= + static_cast<size_t>(std::numeric_limits<Length>::max())); + // Compute the size of the user-accessible buffer inside the chunk. + const Length bufferBytes = + static_cast<Length>(chunkBytes - sizeof(InternalHeader)); + MOZ_ASSERT(bufferBytes >= aMinBufferBytes, + "Not enough space for minimum buffer size"); + // Construct the header at the beginning of the allocated array, with the + // known buffer size. + new (chunkStorage.get()) ProfileBufferChunk(bufferBytes); + // We now have a proper `ProfileBufferChunk` object, create the appropriate + // UniquePtr for it. + UniquePtr<ProfileBufferChunk> chunk{ + reinterpret_cast<ProfileBufferChunk*>(chunkStorage.release())}; + MOZ_ASSERT( + size_t(reinterpret_cast<const char*>( + &chunk.get()->BufferSpan()[bufferBytes - 1]) - + reinterpret_cast<const char*>(chunk.get())) == chunkBytes - 1, + "Buffer span spills out of chunk allocation"); + return chunk; + } + +#ifdef DEBUG + ~ProfileBufferChunk() { + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::InUse); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Full); + MOZ_ASSERT(mInternalHeader.mState == InternalHeader::State::Created || + mInternalHeader.mState == InternalHeader::State::Done || + mInternalHeader.mState == InternalHeader::State::Recycled); + } +#endif + + // Must be called with the first block tail (may be empty), which will be + // skipped if the reader starts with this ProfileBufferChunk. + [[nodiscard]] SpanOfBytes ReserveInitialBlockAsTail(Length aTailSize) { +#ifdef DEBUG + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::InUse); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Full); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Done); + MOZ_ASSERT(mInternalHeader.mState == InternalHeader::State::Created || + mInternalHeader.mState == InternalHeader::State::Recycled); + mInternalHeader.mState = InternalHeader::State::InUse; +#endif + mInternalHeader.mHeader.mOffsetFirstBlock = aTailSize; + mInternalHeader.mHeader.mOffsetPastLastBlock = aTailSize; + return SpanOfBytes(&mBuffer, aTailSize); + } + + struct ReserveReturn { + SpanOfBytes mSpan; + ProfileBufferBlockIndex mBlockRangeIndex; + }; + + // Reserve a block of up to `aBlockSize` bytes, and return a Span to it, and + // its starting index. The actual size may be smaller, if the block cannot fit + // in the remaining space. + [[nodiscard]] ReserveReturn ReserveBlock(Length aBlockSize) { + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Created); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Full); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Done); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Recycled); + MOZ_ASSERT(mInternalHeader.mState == InternalHeader::State::InUse); + MOZ_ASSERT(RangeStart() != 0, + "Expected valid range start before first Reserve()"); + const Length blockOffset = mInternalHeader.mHeader.mOffsetPastLastBlock; + Length reservedSize = aBlockSize; + if (MOZ_UNLIKELY(aBlockSize >= RemainingBytes())) { + reservedSize = RemainingBytes(); +#ifdef DEBUG + mInternalHeader.mState = InternalHeader::State::Full; +#endif + } + mInternalHeader.mHeader.mOffsetPastLastBlock += reservedSize; + mInternalHeader.mHeader.mBlockCount += 1; + return {SpanOfBytes(&mBuffer + blockOffset, reservedSize), + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mInternalHeader.mHeader.mRangeStart + blockOffset)}; + } + + // When a chunk will not be used to store more blocks (because it is full, or + // because the profiler will not add more data), it should be marked "done". + // Access to its content is still allowed. + void MarkDone() { +#ifdef DEBUG + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Created); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Done); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Recycled); + MOZ_ASSERT(mInternalHeader.mState == InternalHeader::State::InUse || + mInternalHeader.mState == InternalHeader::State::Full); + mInternalHeader.mState = InternalHeader::State::Done; +#endif + mInternalHeader.mHeader.mDoneTimeStamp = TimeStamp::NowUnfuzzed(); + } + + // A "Done" chunk may be recycled, to avoid allocating a new one. + void MarkRecycled() { +#ifdef DEBUG + // We also allow Created and already-Recycled chunks to be recycled, this + // way it's easier to recycle chunks when their state is not easily + // trackable. + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::InUse); + MOZ_ASSERT(mInternalHeader.mState != InternalHeader::State::Full); + MOZ_ASSERT(mInternalHeader.mState == InternalHeader::State::Created || + mInternalHeader.mState == InternalHeader::State::Done || + mInternalHeader.mState == InternalHeader::State::Recycled); + mInternalHeader.mState = InternalHeader::State::Recycled; +#endif + // Reset all header fields, in case this recycled chunk gets read. + mInternalHeader.mHeader.Reset(); + } + + // Public header, meant to uniquely identify a chunk, it may be shared with + // other processes to coordinate global memory handling. + struct Header { + explicit Header(Length aBufferBytes) : mBufferBytes(aBufferBytes) {} + + // Reset all members to their as-new values (apart from the buffer size, + // which cannot change), ready for re-use. + void Reset() { + mOffsetFirstBlock = 0; + mOffsetPastLastBlock = 0; + mDoneTimeStamp = TimeStamp{}; + mBlockCount = 0; + mRangeStart = 0; + mProcessId = 0; + } + + // Note: Part of the ordering of members below is to avoid unnecessary + // padding. + + // Members managed by the ProfileBufferChunk. + + // Offset of the first block (past the initial tail block, which may be 0). + Length mOffsetFirstBlock = 0; + // Offset past the last byte of the last reserved block + // It may be past mBufferBytes when last block continues in the next + // ProfileBufferChunk. It may be before mBufferBytes if ProfileBufferChunk + // is marked "Done" before the end is reached. + Length mOffsetPastLastBlock = 0; + // Timestamp when buffer is "Done" (which happens when the last block is + // written). This will be used to find and discard the oldest + // ProfileBufferChunk. + TimeStamp mDoneTimeStamp; + // Number of bytes in the buffer, set once at construction time. + const Length mBufferBytes; + // Number of reserved blocks (including final one even if partial, but + // excluding initial tail). + Length mBlockCount = 0; + + // Meta-data set by the user. + + // Index of the first byte of this ProfileBufferChunk, relative to all + // Chunks for this process. Index 0 is reserved as nullptr-like index, + // mRangeStart should be set to a non-0 value before the first `Reserve()`. + ProfileBufferIndex mRangeStart = 0; + // Process writing to this ProfileBufferChunk. + int mProcessId = 0; + + // A bit of spare space (necessary here because of the alignment due to + // other members), may be later repurposed for extra data. + const int mPADDING = 0; + }; + + [[nodiscard]] const Header& ChunkHeader() const { + return mInternalHeader.mHeader; + } + + [[nodiscard]] Length BufferBytes() const { + return ChunkHeader().mBufferBytes; + } + + // Total size of the chunk (buffer + header). + [[nodiscard]] Length ChunkBytes() const { + return static_cast<Length>(sizeof(InternalHeader)) + BufferBytes(); + } + + // Size of external resources, in this case all the following chunks. + [[nodiscard]] size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const { + const ProfileBufferChunk* const next = GetNext(); + return next ? next->SizeOfIncludingThis(aMallocSizeOf) : 0; + } + + // Size of this chunk and all following ones. + [[nodiscard]] size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const { + // Just in case `aMallocSizeOf` falls back on just `sizeof`, make sure we + // account for at least the actual Chunk requested allocation size. + return std::max<size_t>(aMallocSizeOf(this), ChunkBytes()) + + SizeOfExcludingThis(aMallocSizeOf); + } + + [[nodiscard]] Length RemainingBytes() const { + return BufferBytes() - OffsetPastLastBlock(); + } + + [[nodiscard]] Length OffsetFirstBlock() const { + return ChunkHeader().mOffsetFirstBlock; + } + + [[nodiscard]] Length OffsetPastLastBlock() const { + return ChunkHeader().mOffsetPastLastBlock; + } + + [[nodiscard]] Length BlockCount() const { return ChunkHeader().mBlockCount; } + + [[nodiscard]] int ProcessId() const { return ChunkHeader().mProcessId; } + + void SetProcessId(int aProcessId) { + mInternalHeader.mHeader.mProcessId = aProcessId; + } + + // Global range index at the start of this Chunk. + [[nodiscard]] ProfileBufferIndex RangeStart() const { + return ChunkHeader().mRangeStart; + } + + void SetRangeStart(ProfileBufferIndex aRangeStart) { + mInternalHeader.mHeader.mRangeStart = aRangeStart; + } + + // Get a read-only Span to the buffer. It is up to the caller to decypher the + // contents, based on known offsets and the internal block structure. + [[nodiscard]] Span<const Byte> BufferSpan() const { + return Span<const Byte>(&mBuffer, BufferBytes()); + } + + [[nodiscard]] Byte ByteAt(Length aOffset) const { + MOZ_ASSERT(aOffset < OffsetPastLastBlock()); + return *(&mBuffer + aOffset); + } + + [[nodiscard]] ProfileBufferChunk* GetNext() { + return mInternalHeader.mNext.get(); + } + [[nodiscard]] const ProfileBufferChunk* GetNext() const { + return mInternalHeader.mNext.get(); + } + + [[nodiscard]] UniquePtr<ProfileBufferChunk> ReleaseNext() { + return std::move(mInternalHeader.mNext); + } + + void InsertNext(UniquePtr<ProfileBufferChunk>&& aChunk) { + if (!aChunk) { + return; + } + aChunk->SetLast(ReleaseNext()); + mInternalHeader.mNext = std::move(aChunk); + } + + // Find the last chunk in this chain (it may be `this`). + [[nodiscard]] ProfileBufferChunk* Last() { + ProfileBufferChunk* chunk = this; + for (;;) { + ProfileBufferChunk* next = chunk->GetNext(); + if (!next) { + return chunk; + } + chunk = next; + } + } + [[nodiscard]] const ProfileBufferChunk* Last() const { + const ProfileBufferChunk* chunk = this; + for (;;) { + const ProfileBufferChunk* next = chunk->GetNext(); + if (!next) { + return chunk; + } + chunk = next; + } + } + + void SetLast(UniquePtr<ProfileBufferChunk>&& aChunk) { + if (!aChunk) { + return; + } + Last()->mInternalHeader.mNext = std::move(aChunk); + } + + // Join two possibly-null chunk lists. + [[nodiscard]] static UniquePtr<ProfileBufferChunk> Join( + UniquePtr<ProfileBufferChunk>&& aFirst, + UniquePtr<ProfileBufferChunk>&& aLast) { + if (aFirst) { + aFirst->SetLast(std::move(aLast)); + return std::move(aFirst); + } + return std::move(aLast); + } + +#ifdef DEBUG + void Dump(std::FILE* aFile = stdout) const { + fprintf(aFile, + "Chunk[%p] chunkSize=%u bufferSize=%u state=%s rangeStart=%u " + "firstBlockOffset=%u offsetPastLastBlock=%u blockCount=%u", + this, unsigned(ChunkBytes()), unsigned(BufferBytes()), + mInternalHeader.StateString(), unsigned(RangeStart()), + unsigned(OffsetFirstBlock()), unsigned(OffsetPastLastBlock()), + unsigned(BlockCount())); + const auto len = OffsetPastLastBlock(); + constexpr unsigned columns = 16; + unsigned char ascii[columns + 1]; + ascii[columns] = '\0'; + for (Length i = 0; i < len; ++i) { + if (i % columns == 0) { + fprintf(aFile, "\n %4u=0x%03x:", unsigned(i), unsigned(i)); + for (unsigned a = 0; a < columns; ++a) { + ascii[a] = ' '; + } + } + unsigned char sep = ' '; + if (i == OffsetFirstBlock()) { + if (i == OffsetPastLastBlock()) { + sep = '#'; + } else { + sep = '['; + } + } else if (i == OffsetPastLastBlock()) { + sep = ']'; + } + unsigned char c = *(&mBuffer + i); + fprintf(aFile, "%c%02x", sep, c); + + if (i == len - 1) { + if (i + 1 == OffsetPastLastBlock()) { + // Special case when last block ends right at the end. + fprintf(aFile, "]"); + } else { + fprintf(aFile, " "); + } + } else if (i % columns == columns - 1) { + fprintf(aFile, " "); + } + + ascii[i % columns] = (c >= ' ' && c <= '~') ? c : '.'; + + if (i % columns == columns - 1) { + fprintf(aFile, " %s", ascii); + } + } + + if (len % columns < columns - 1) { + for (Length i = len % columns; i < columns; ++i) { + fprintf(aFile, " "); + } + fprintf(aFile, " %s", ascii); + } + + fprintf(aFile, "\n"); + } +#endif // DEBUG + + private: + // ProfileBufferChunk constructor. Use static `Create()` to allocate and + // construct a ProfileBufferChunk. + explicit ProfileBufferChunk(Length aBufferBytes) + : mInternalHeader(aBufferBytes) {} + + // This internal header starts with the public `Header`, and adds some data + // only necessary for local handling. + // This encapsulation is also necessary to perform placement-new in + // `Create()`. + struct InternalHeader { + explicit InternalHeader(Length aBufferBytes) : mHeader(aBufferBytes) {} + + Header mHeader; + UniquePtr<ProfileBufferChunk> mNext; + +#ifdef DEBUG + enum class State { + Created, // Self-set. Just constructed, waiting for initial block tail. + InUse, // Ready to accept blocks. + Full, // Self-set. Blocks reach the end (or further). + Done, // Blocks won't be added anymore. + Recycled // Still full of data, but expecting an initial block tail. + }; + + State mState = State::Created; + // Transition table: (X=unexpected) + // Method \ State Created InUse Full Done Recycled + // ReserveInitialBlockAsTail InUse X X X InUse + // Reserve X InUse/Full X X X + // MarkDone X Done Done X X + // MarkRecycled X X X Recycled X + // destructor ok X X ok ok + + const char* StateString() const { + switch (mState) { + case State::Created: + return "Created"; + case State::InUse: + return "InUse"; + case State::Full: + return "Full"; + case State::Done: + return "Done"; + case State::Recycled: + return "Recycled"; + default: + return "?"; + } + } +#else // DEBUG + const char* StateString() const { return "(non-DEBUG)"; } +#endif + }; + + InternalHeader mInternalHeader; + + // KEEP THIS LAST! + // First byte of the buffer. Note that ProfileBufferChunk::Create allocates a + // bigger block, such that `mBuffer` is the first of `mBufferBytes` available + // bytes. + // The initialization is not strictly needed, because bytes should only be + // read after they have been written and `mOffsetPastLastBlock` has been + // updated. However: + // - Reviewbot complains that it's not initialized. + // - It's cheap to initialize one byte. + // - In the worst case (reading does happen), zero is not a valid entry size + // and should get caught in entry readers. + Byte mBuffer = '\0'; +}; + +} // namespace mozilla + +#endif // ProfileBufferChunk_h |