DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (a177dd13e984)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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/. */

#include "MemoryBlockCache.h"

#include "mozilla/Atomics.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/Logging.h"
#include "mozilla/Services.h"
#include "mozilla/StaticPrefs_media.h"
#include "nsWeakReference.h"
#include "prsystem.h"

namespace mozilla {

#undef LOG
LazyLogModule gMemoryBlockCacheLog("MemoryBlockCache");
#define LOG(x, ...) \
  MOZ_LOG(gMemoryBlockCacheLog, LogLevel::Debug, ("%p " x, this, ##__VA_ARGS__))

// Combined sizes of all MemoryBlockCache buffers.
// Initialized to 0 by non-local static initialization.
// Increases when a buffer grows (during initialization or unexpected OOB
// writes), decreases when a MemoryBlockCache (with its buffer) is destroyed.
static Atomic<size_t> gCombinedSizes;

static int32_t CalculateMaxBlocks(int64_t aContentLength) {
  int64_t maxSize = int64_t(StaticPrefs::media_memory_cache_max_size()) * 1024;
  MOZ_ASSERT(aContentLength <= maxSize);
  MOZ_ASSERT(maxSize % MediaBlockCacheBase::BLOCK_SIZE == 0);
  // Note: It doesn't matter if calculations overflow, Init() would later fail.
  // We want at least enough blocks to contain the original content length.
  const int32_t requiredBlocks = maxSize / MediaBlockCacheBase::BLOCK_SIZE;
  // Allow at least 1s of ultra HD (25Mbps).
  const int32_t workableBlocks =
      25 * 1024 * 1024 / 8 / MediaBlockCacheBase::BLOCK_SIZE;
  return std::max(requiredBlocks, workableBlocks);
}

MemoryBlockCache::MemoryBlockCache(int64_t aContentLength)
    // Buffer whole blocks.
    : mInitialContentLength((aContentLength >= 0) ? size_t(aContentLength) : 0),
      mMaxBlocks(CalculateMaxBlocks(aContentLength)),
      mMutex("MemoryBlockCache"),
      mHasGrown(false) {
  if (aContentLength <= 0) {
    LOG("MemoryBlockCache() MEMORYBLOCKCACHE_ERRORS='InitUnderuse'");
  }
}

MemoryBlockCache::~MemoryBlockCache() {
  size_t sizes = static_cast<size_t>(gCombinedSizes -= mBuffer.Length());
  LOG("~MemoryBlockCache() - destroying buffer of size %zu; combined sizes now "
      "%zu",
      mBuffer.Length(), sizes);
}

bool MemoryBlockCache::EnsureBufferCanContain(size_t aContentLength) {
  mMutex.AssertCurrentThreadOwns();
  if (aContentLength == 0) {
    return true;
  }
  const size_t initialLength = mBuffer.Length();
  const size_t desiredLength =
      ((aContentLength - 1) / BLOCK_SIZE + 1) * BLOCK_SIZE;
  if (initialLength >= desiredLength) {
    // Already large enough.
    return true;
  }
  // Need larger buffer. If we are allowed more memory, attempt to re-allocate.
  const size_t extra = desiredLength - initialLength;
  // Only check the very first allocation against the combined MemoryBlockCache
  // limit. Further growths will always be allowed, assuming MediaCache won't
  // go over GetMaxBlocks() by too much.
  if (initialLength == 0) {
    // Note: There is a small race between testing `atomic + extra > limit` and
    // committing to it with `atomic += extra` below; but this is acceptable, as
    // in the worst case it may allow a small number of buffers to go past the
    // limit.
    // The alternative would have been to reserve the space first with
    // `atomic += extra` and then undo it with `atomic -= extra` in case of
    // failure; but this would have meant potentially preventing other (small
    // but successful) allocations.
    static const size_t sysmem =
        std::max<size_t>(PR_GetPhysicalMemorySize(), 32 * 1024 * 1024);
    const size_t limit = std::min(
        size_t(StaticPrefs::media_memory_caches_combined_limit_kb()) * 1024,
        sysmem * StaticPrefs::media_memory_caches_combined_limit_pc_sysmem() /
            100);
    const size_t currentSizes = static_cast<size_t>(gCombinedSizes);
    if (currentSizes + extra > limit) {
      LOG("EnsureBufferCanContain(%zu) - buffer size %zu, wanted + %zu = %zu;"
          " combined sizes %zu + %zu > limit %zu",
          aContentLength, initialLength, extra, desiredLength, currentSizes,
          extra, limit);
      return false;
    }
  }
  if (!mBuffer.SetLength(desiredLength, mozilla::fallible)) {
    LOG("EnsureBufferCanContain(%zu) - buffer size %zu, wanted + %zu = %zu, "
        "allocation failed",
        aContentLength, initialLength, extra, desiredLength);
    return false;
  }
  MOZ_ASSERT(mBuffer.Length() == desiredLength);
  const size_t capacity = mBuffer.Capacity();
  const size_t extraCapacity = capacity - desiredLength;
  if (extraCapacity != 0) {
    // Our buffer was given a larger capacity than the requested length, we may
    // as well claim that extra capacity, both for our accounting, and to
    // possibly bypass some future growths that would fit in this new capacity.
    mBuffer.SetLength(capacity);
  }
  mHasGrown = true;
  return true;
}

nsresult MemoryBlockCache::Init() {
  LOG("Init()");
  MutexAutoLock lock(mMutex);
  MOZ_ASSERT(mBuffer.IsEmpty());
  // Attempt to pre-allocate buffer for expected content length.
  if (!EnsureBufferCanContain(mInitialContentLength)) {
    LOG("Init() MEMORYBLOCKCACHE_ERRORS='InitAllocation'");
    return NS_ERROR_FAILURE;
  }
  return NS_OK;
}

void MemoryBlockCache::Flush() {
  LOG("Flush()");
  MutexAutoLock lock(mMutex);
  MOZ_ASSERT(mBuffer.Length() >= mInitialContentLength);
  memset(mBuffer.Elements(), 0, mBuffer.Length());
  mHasGrown = false;
}

nsresult MemoryBlockCache::WriteBlock(uint32_t aBlockIndex,
                                      Span<const uint8_t> aData1,
                                      Span<const uint8_t> aData2) {
  MutexAutoLock lock(mMutex);

  size_t offset = BlockIndexToOffset(aBlockIndex);
  if (offset + aData1.Length() + aData2.Length() > mBuffer.Length() &&
      !mHasGrown) {
    LOG("WriteBlock() MEMORYBLOCKCACHE_ERRORS='WriteBlockOverflow'");
  }
  if (!EnsureBufferCanContain(offset + aData1.Length() + aData2.Length())) {
    LOG("WriteBlock() MEMORYBLOCKCACHE_ERRORS='WriteBlockCannotGrow'");
    return NS_ERROR_FAILURE;
  }

  memcpy(mBuffer.Elements() + offset, aData1.Elements(), aData1.Length());
  if (aData2.Length() > 0) {
    memcpy(mBuffer.Elements() + offset + aData1.Length(), aData2.Elements(),
           aData2.Length());
  }

  return NS_OK;
}

nsresult MemoryBlockCache::Read(int64_t aOffset, uint8_t* aData,
                                int32_t aLength, int32_t* aBytes) {
  MutexAutoLock lock(mMutex);

  MOZ_ASSERT(aOffset >= 0);
  if (aOffset + aLength > int64_t(mBuffer.Length())) {
    LOG("Read() MEMORYBLOCKCACHE_ERRORS='ReadOverrun'");
    return NS_ERROR_FAILURE;
  }

  memcpy(aData, mBuffer.Elements() + aOffset, aLength);
  *aBytes = aLength;

  return NS_OK;
}

nsresult MemoryBlockCache::MoveBlock(int32_t aSourceBlockIndex,
                                     int32_t aDestBlockIndex) {
  MutexAutoLock lock(mMutex);

  size_t sourceOffset = BlockIndexToOffset(aSourceBlockIndex);
  size_t destOffset = BlockIndexToOffset(aDestBlockIndex);
  if (sourceOffset + BLOCK_SIZE > mBuffer.Length()) {
    LOG("MoveBlock() MEMORYBLOCKCACHE_ERRORS='MoveBlockSourceOverrun'");
    return NS_ERROR_FAILURE;
  }
  if (destOffset + BLOCK_SIZE > mBuffer.Length() && !mHasGrown) {
    LOG("MoveBlock() MEMORYBLOCKCACHE_ERRORS='MoveBlockDestOverflow'");
  }
  if (!EnsureBufferCanContain(destOffset + BLOCK_SIZE)) {
    LOG("MoveBlock() MEMORYBLOCKCACHE_ERRORS='MoveBlockCannotGrow'");
    return NS_ERROR_FAILURE;
  }

  memcpy(mBuffer.Elements() + destOffset, mBuffer.Elements() + sourceOffset,
         BLOCK_SIZE);

  return NS_OK;
}

}  // End namespace mozilla.

// avoid redefined macro in unified build
#undef LOG