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+/* -*- 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 ProfileBufferChunkManagerWithLocalLimit_h
+#define ProfileBufferChunkManagerWithLocalLimit_h
+
+#include "BaseProfiler.h"
+#include "mozilla/BaseProfilerDetail.h"
+#include "mozilla/ProfileBufferChunkManager.h"
+#include "mozilla/ProfileBufferControlledChunkManager.h"
+#include "mozilla/mozalloc.h"
+
+#include <utility>
+
+namespace mozilla {
+
+// Manages the Chunks for this process in a thread-safe manner, with a maximum
+// size per process.
+//
+// "Unreleased" chunks are not owned here, only "released" chunks can be
+// destroyed or recycled when reaching the memory limit, so it is theoretically
+// possible to break that limit, if:
+// - The user of this class doesn't release their chunks, AND/OR
+// - The limit is too small (e.g., smaller than 2 or 3 chunks, which should be
+// the usual number of unreleased chunks in flight).
+// In this case, it just means that we will use more memory than allowed,
+// potentially risking OOMs. Hopefully this shouldn't happen in real code,
+// assuming that the user is doing the right thing and releasing chunks ASAP,
+// and that the memory limit is reasonably large.
+class ProfileBufferChunkManagerWithLocalLimit final
+ : public ProfileBufferChunkManager,
+ public ProfileBufferControlledChunkManager {
+ public:
+ using Length = ProfileBufferChunk::Length;
+
+ // MaxTotalBytes: Maximum number of bytes allocated in all local Chunks.
+ // ChunkMinBufferBytes: Minimum number of user-available bytes in each Chunk.
+ // Note that Chunks use a bit more memory for their header.
+ explicit ProfileBufferChunkManagerWithLocalLimit(size_t aMaxTotalBytes,
+ Length aChunkMinBufferBytes)
+ : mMaxTotalBytes(aMaxTotalBytes),
+ mChunkMinBufferBytes(aChunkMinBufferBytes) {}
+
+ ~ProfileBufferChunkManagerWithLocalLimit() {
+ if (mUpdateCallback) {
+ // Signal the end of this callback.
+ std::move(mUpdateCallback)(Update(nullptr));
+ }
+ }
+
+ [[nodiscard]] size_t MaxTotalSize() const final {
+ // `mMaxTotalBytes` is `const` so there is no need to lock the mutex.
+ return mMaxTotalBytes;
+ }
+
+ [[nodiscard]] size_t TotalSize() const { return mTotalBytes; }
+
+ [[nodiscard]] UniquePtr<ProfileBufferChunk> GetChunk() final {
+ AUTO_PROFILER_STATS(Local_GetChunk);
+
+ ChunkAndUpdate chunkAndUpdate = [&]() {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ return GetChunk(lock);
+ }();
+
+ baseprofiler::detail::BaseProfilerAutoLock lock(mUpdateCallbackMutex);
+ if (mUpdateCallback && !chunkAndUpdate.second.IsNotUpdate()) {
+ mUpdateCallback(std::move(chunkAndUpdate.second));
+ }
+
+ return std::move(chunkAndUpdate.first);
+ }
+
+ void RequestChunk(std::function<void(UniquePtr<ProfileBufferChunk>)>&&
+ aChunkReceiver) final {
+ AUTO_PROFILER_STATS(Local_RequestChunk);
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ if (mChunkReceiver) {
+ // We already have a chunk receiver, meaning a request is pending.
+ return;
+ }
+ // Store the chunk receiver. This indicates that a request is pending, and
+ // it will be handled in the next `FulfillChunkRequests()` call.
+ mChunkReceiver = std::move(aChunkReceiver);
+ }
+
+ void FulfillChunkRequests() final {
+ AUTO_PROFILER_STATS(Local_FulfillChunkRequests);
+ std::function<void(UniquePtr<ProfileBufferChunk>)> chunkReceiver;
+ ChunkAndUpdate chunkAndUpdate = [&]() -> ChunkAndUpdate {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ if (!mChunkReceiver) {
+ // No receiver means no pending request, we're done.
+ return {};
+ }
+ // Otherwise there is a request, extract the receiver to call below.
+ std::swap(chunkReceiver, mChunkReceiver);
+ MOZ_ASSERT(!mChunkReceiver, "mChunkReceiver should have been emptied");
+ // And allocate the requested chunk. This may fail, it's fine, we're
+ // letting the receiver know about it.
+ AUTO_PROFILER_STATS(Local_FulfillChunkRequests_GetChunk);
+ return GetChunk(lock);
+ }();
+
+ if (chunkReceiver) {
+ {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mUpdateCallbackMutex);
+ if (mUpdateCallback && !chunkAndUpdate.second.IsNotUpdate()) {
+ mUpdateCallback(std::move(chunkAndUpdate.second));
+ }
+ }
+
+ // Invoke callback outside of lock, so that it can use other chunk manager
+ // functions if needed.
+ // Note that this means there could be a race, where another request
+ // happens now and even gets fulfilled before this one is! It should be
+ // rare, and shouldn't be a problem anyway, the user will still get their
+ // requested chunks, new/recycled chunks look the same so their order
+ // doesn't matter.
+ std::move(chunkReceiver)(std::move(chunkAndUpdate.first));
+ }
+ }
+
+ void ReleaseChunk(UniquePtr<ProfileBufferChunk> aChunk) final {
+ if (!aChunk) {
+ return;
+ }
+
+ MOZ_RELEASE_ASSERT(!aChunk->GetNext(), "ReleaseChunk only accepts 1 chunk");
+ MOZ_RELEASE_ASSERT(!aChunk->ChunkHeader().mDoneTimeStamp.IsNull(),
+ "Released chunk should have a 'Done' timestamp");
+
+ Update update = [&]() {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ MOZ_ASSERT(mUser, "Not registered yet");
+ // Keep a pointer to the first newly-released chunk, so we can use it to
+ // prepare an update (after `aChunk` is moved-from).
+ const ProfileBufferChunk* const newlyReleasedChunk = aChunk.get();
+ // Transfer the chunk size from the unreleased bucket to the released one.
+ mUnreleasedBufferBytes -= aChunk->BufferBytes();
+ mReleasedBufferBytes += aChunk->BufferBytes();
+ if (!mReleasedChunks) {
+ // No other released chunks at the moment, we're starting the list.
+ MOZ_ASSERT(mReleasedBufferBytes == aChunk->BufferBytes());
+ mReleasedChunks = std::move(aChunk);
+ } else {
+ // Insert aChunk in mReleasedChunks to keep done-timestamp order.
+ const TimeStamp& releasedChunkDoneTimeStamp =
+ aChunk->ChunkHeader().mDoneTimeStamp;
+ if (releasedChunkDoneTimeStamp <
+ mReleasedChunks->ChunkHeader().mDoneTimeStamp) {
+ // aChunk is the oldest -> Insert at the beginning.
+ aChunk->SetLast(std::move(mReleasedChunks));
+ mReleasedChunks = std::move(aChunk);
+ } else {
+ // Go through the already-released chunk list, and insert aChunk
+ // before the first younger released chunk, or at the end.
+ ProfileBufferChunk* chunk = mReleasedChunks.get();
+ for (;;) {
+ ProfileBufferChunk* const nextChunk = chunk->GetNext();
+ if (!nextChunk || releasedChunkDoneTimeStamp <
+ nextChunk->ChunkHeader().mDoneTimeStamp) {
+ // Either we're at the last released chunk, or the next released
+ // chunk is younger -> Insert right after this released chunk.
+ chunk->InsertNext(std::move(aChunk));
+ break;
+ }
+ chunk = nextChunk;
+ }
+ }
+ }
+
+ return Update(mUnreleasedBufferBytes, mReleasedBufferBytes,
+ mReleasedChunks.get(), newlyReleasedChunk);
+ }();
+
+ baseprofiler::detail::BaseProfilerAutoLock lock(mUpdateCallbackMutex);
+ if (mUpdateCallback && !update.IsNotUpdate()) {
+ mUpdateCallback(std::move(update));
+ }
+ }
+
+ void SetChunkDestroyedCallback(
+ std::function<void(const ProfileBufferChunk&)>&& aChunkDestroyedCallback)
+ final {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ MOZ_ASSERT(mUser, "Not registered yet");
+ mChunkDestroyedCallback = std::move(aChunkDestroyedCallback);
+ }
+
+ [[nodiscard]] UniquePtr<ProfileBufferChunk> GetExtantReleasedChunks() final {
+ UniquePtr<ProfileBufferChunk> chunks;
+ size_t unreleasedBufferBytes = [&]() {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ MOZ_ASSERT(mUser, "Not registered yet");
+ mReleasedBufferBytes = 0;
+ chunks = std::move(mReleasedChunks);
+ return mUnreleasedBufferBytes;
+ }();
+
+ baseprofiler::detail::BaseProfilerAutoLock lock(mUpdateCallbackMutex);
+ if (mUpdateCallback) {
+ mUpdateCallback(Update(unreleasedBufferBytes, 0, nullptr, nullptr));
+ }
+
+ return chunks;
+ }
+
+ void ForgetUnreleasedChunks() final {
+ Update update = [&]() {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ MOZ_ASSERT(mUser, "Not registered yet");
+ mUnreleasedBufferBytes = 0;
+ return Update(0, mReleasedBufferBytes, mReleasedChunks.get(), nullptr);
+ }();
+ baseprofiler::detail::BaseProfilerAutoLock lock(mUpdateCallbackMutex);
+ if (mUpdateCallback) {
+ mUpdateCallback(std::move(update));
+ }
+ }
+
+ [[nodiscard]] size_t SizeOfExcludingThis(
+ MallocSizeOf aMallocSizeOf) const final {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ return SizeOfExcludingThis(aMallocSizeOf, lock);
+ }
+
+ [[nodiscard]] size_t SizeOfIncludingThis(
+ MallocSizeOf aMallocSizeOf) const final {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ MOZ_ASSERT(mUser, "Not registered yet");
+ return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf, lock);
+ }
+
+ void SetUpdateCallback(UpdateCallback&& aUpdateCallback) final {
+ {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mUpdateCallbackMutex);
+ if (mUpdateCallback) {
+ // Signal the end of the previous callback.
+ std::move(mUpdateCallback)(Update(nullptr));
+ mUpdateCallback = nullptr;
+ }
+ }
+
+ if (aUpdateCallback) {
+ Update initialUpdate = [&]() {
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ return Update(mUnreleasedBufferBytes, mReleasedBufferBytes,
+ mReleasedChunks.get(), nullptr);
+ }();
+
+ baseprofiler::detail::BaseProfilerAutoLock lock(mUpdateCallbackMutex);
+ MOZ_ASSERT(!mUpdateCallback, "Only one update callback allowed");
+ mUpdateCallback = std::move(aUpdateCallback);
+ mUpdateCallback(std::move(initialUpdate));
+ }
+ }
+
+ void DestroyChunksAtOrBefore(TimeStamp aDoneTimeStamp) final {
+ MOZ_ASSERT(!aDoneTimeStamp.IsNull());
+ baseprofiler::detail::BaseProfilerAutoLock lock(mMutex);
+ for (;;) {
+ if (!mReleasedChunks) {
+ // We don't own any released chunks (anymore), we're done.
+ break;
+ }
+ if (mReleasedChunks->ChunkHeader().mDoneTimeStamp > aDoneTimeStamp) {
+ // The current chunk is strictly after the given timestamp, we're done.
+ break;
+ }
+ // We've found a chunk at or before the timestamp, discard it.
+ DiscardOldestReleasedChunk(lock);
+ }
+ }
+
+ protected:
+ const ProfileBufferChunk* PeekExtantReleasedChunksAndLock() final
+ MOZ_CAPABILITY_ACQUIRE(mMutex) {
+ mMutex.Lock();
+ MOZ_ASSERT(mUser, "Not registered yet");
+ return mReleasedChunks.get();
+ }
+ void UnlockAfterPeekExtantReleasedChunks() final
+ MOZ_CAPABILITY_RELEASE(mMutex) {
+ mMutex.Unlock();
+ }
+
+ private:
+ size_t MaybeRecycleChunkAndGetDeallocatedSize(
+ UniquePtr<ProfileBufferChunk>&& chunk,
+ const baseprofiler::detail::BaseProfilerAutoLock& aLock) {
+ // Try to recycle big-enough chunks. (All chunks should have the same size,
+ // but it's a cheap test and may allow future adjustments based on actual
+ // data rate.)
+ if (chunk->BufferBytes() >= mChunkMinBufferBytes) {
+ // We keep up to two recycled chunks at any time.
+ if (!mRecycledChunks) {
+ mRecycledChunks = std::move(chunk);
+ return 0;
+ } else if (!mRecycledChunks->GetNext()) {
+ mRecycledChunks->InsertNext(std::move(chunk));
+ return 0;
+ }
+ }
+ return moz_malloc_usable_size(chunk.get());
+ }
+
+ UniquePtr<ProfileBufferChunk> TakeRecycledChunk(
+ const baseprofiler::detail::BaseProfilerAutoLock& aLock) {
+ UniquePtr<ProfileBufferChunk> recycled;
+ if (mRecycledChunks) {
+ recycled = std::exchange(mRecycledChunks, mRecycledChunks->ReleaseNext());
+ recycled->MarkRecycled();
+ }
+ return recycled;
+ }
+
+ void DiscardOldestReleasedChunk(
+ const baseprofiler::detail::BaseProfilerAutoLock& aLock) {
+ MOZ_ASSERT(!!mReleasedChunks);
+ UniquePtr<ProfileBufferChunk> oldest =
+ std::exchange(mReleasedChunks, mReleasedChunks->ReleaseNext());
+ mReleasedBufferBytes -= oldest->BufferBytes();
+ if (mChunkDestroyedCallback) {
+ // Inform the user that we're going to destroy this chunk.
+ mChunkDestroyedCallback(*oldest);
+ }
+
+ mTotalBytes -=
+ MaybeRecycleChunkAndGetDeallocatedSize(std::move(oldest), aLock);
+ }
+
+ using ChunkAndUpdate = std::pair<UniquePtr<ProfileBufferChunk>, Update>;
+ [[nodiscard]] ChunkAndUpdate GetChunk(
+ const baseprofiler::detail::BaseProfilerAutoLock& aLock) {
+ MOZ_ASSERT(mUser, "Not registered yet");
+ // After this function, the total memory consumption will be the sum of:
+ // - Bytes from released (i.e., full) chunks,
+ // - Bytes from unreleased (still in use) chunks,
+ // - Bytes from the chunk we want to create/recycle. (Note that we don't
+ // count the extra bytes of chunk header, and of extra allocation ability,
+ // for the new chunk, as it's assumed to be negligible compared to the
+ // total memory limit.)
+ // If this total is higher than the local limit, we'll want to destroy
+ // the oldest released chunks until we're under the limit; if any, we may
+ // recycle one of them to avoid a deallocation followed by an allocation.
+ while (mReleasedBufferBytes + mUnreleasedBufferBytes +
+ mChunkMinBufferBytes >=
+ mMaxTotalBytes &&
+ !!mReleasedChunks) {
+ // We have reached the local limit, discard the oldest released chunk.
+ DiscardOldestReleasedChunk(aLock);
+ }
+
+ // Extract the recycled chunk, if any.
+ ChunkAndUpdate chunkAndUpdate{TakeRecycledChunk(aLock), Update()};
+ UniquePtr<ProfileBufferChunk>& chunk = chunkAndUpdate.first;
+
+ if (!chunk) {
+ // No recycled chunk -> Create a chunk now. (This could still fail.)
+ chunk = ProfileBufferChunk::Create(mChunkMinBufferBytes);
+ mTotalBytes += moz_malloc_usable_size(chunk.get());
+ }
+
+ if (chunk) {
+ // We do have a chunk (recycled or new), record its size as "unreleased".
+ mUnreleasedBufferBytes += chunk->BufferBytes();
+
+ chunkAndUpdate.second =
+ Update(mUnreleasedBufferBytes, mReleasedBufferBytes,
+ mReleasedChunks.get(), nullptr);
+ }
+
+ return chunkAndUpdate;
+ }
+
+ [[nodiscard]] size_t SizeOfExcludingThis(
+ MallocSizeOf aMallocSizeOf,
+ const baseprofiler::detail::BaseProfilerAutoLock&) const {
+ MOZ_ASSERT(mUser, "Not registered yet");
+ size_t size = 0;
+ if (mReleasedChunks) {
+ size += mReleasedChunks->SizeOfIncludingThis(aMallocSizeOf);
+ }
+ if (mRecycledChunks) {
+ size += mRecycledChunks->SizeOfIncludingThis(aMallocSizeOf);
+ }
+ // Note: Missing size of std::function external resources (if any).
+ return size;
+ }
+
+ // Maxumum number of bytes that should be used by all unreleased and released
+ // chunks. Note that only released chunks can be destroyed here, so it is the
+ // responsibility of the user to properly release their chunks when possible.
+ const size_t mMaxTotalBytes;
+
+ // Minimum number of bytes that new chunks should be able to store.
+ // Used when calling `ProfileBufferChunk::Create()`.
+ const Length mChunkMinBufferBytes;
+
+ // Mutex guarding the following members.
+ mutable baseprofiler::detail::BaseProfilerMutex mMutex;
+
+ // Number of bytes currently held in chunks that have been given away (through
+ // `GetChunk` or `RequestChunk`) and not released yet.
+ size_t mUnreleasedBufferBytes = 0;
+
+ // Number of bytes currently held in chunks that have been released and stored
+ // in `mReleasedChunks` below.
+ size_t mReleasedBufferBytes = 0;
+
+ // Total allocated size (used to substract it from memory counters).
+ size_t mTotalBytes = 0;
+
+ // List of all released chunks. The oldest one should be at the start of the
+ // list, and may be destroyed or recycled when the memory limit is reached.
+ UniquePtr<ProfileBufferChunk> mReleasedChunks;
+
+ // This may hold chunks that were released then slated for destruction, they
+ // will be reused next time an allocation would have been needed.
+ UniquePtr<ProfileBufferChunk> mRecycledChunks;
+
+ // Optional callback used to notify the user when a chunk is about to be
+ // destroyed or recycled. (The data content is always destroyed, but the chunk
+ // container may be reused.)
+ std::function<void(const ProfileBufferChunk&)> mChunkDestroyedCallback;
+
+ // Callback set from `RequestChunk()`, until it is serviced in
+ // `FulfillChunkRequests()`. There can only be one request in flight.
+ std::function<void(UniquePtr<ProfileBufferChunk>)> mChunkReceiver;
+
+ // Separate mutex guarding mUpdateCallback, so that it may be invoked outside
+ // of the main buffer `mMutex`.
+ mutable baseprofiler::detail::BaseProfilerMutex mUpdateCallbackMutex;
+
+ UpdateCallback mUpdateCallback;
+};
+
+} // namespace mozilla
+
+#endif // ProfileBufferChunkManagerWithLocalLimit_h