content/child/child_discardable_shared_memory_manager.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/child/child_discardable_shared_memory_manager.h"
   6
   7 #include "base/atomic_sequence_num.h"
   8 #include "base/bind.h"
   9 #include "base/debug/crash_logging.h"
  10 #include "base/memory/discardable_memory.h"
  11 #include "base/memory/discardable_shared_memory.h"
  12 #include "base/metrics/histogram.h"
  13 #include "base/process/memory.h"
  14 #include "base/process/process_metrics.h"
  15 #include "base/strings/string_number_conversions.h"
  16 #include "base/trace_event/trace_event.h"
  17 #include "content/common/child_process_messages.h"
  18
  19 namespace content {
  20 namespace {
  21
  22 // Default allocation size.
  23 #if defined(OS_ANDROID)
  24 // Larger allocation size on Android to avoid reaching the FD-limit.
  25 const size_t kAllocationSize = 32 * 1024 * 1024;
  26 #else
  27 const size_t kAllocationSize = 4 * 1024 * 1024;
  28 #endif
  29
  30 // Global atomic to generate unique discardable shared memory IDs.
  31 base::StaticAtomicSequenceNumber g_next_discardable_shared_memory_id;
  32
  33 class DiscardableMemoryImpl : public base::DiscardableMemory {
  34  public:
  35   DiscardableMemoryImpl(ChildDiscardableSharedMemoryManager* manager,
  36                         scoped_ptr<DiscardableSharedMemoryHeap::Span> span)
  37       : manager_(manager), span_(span.Pass()), is_locked_(true) {}
  38
  39   ~DiscardableMemoryImpl() override {
  40     if (is_locked_)
  41       manager_->UnlockSpan(span_.get());
  42
  43     manager_->ReleaseSpan(span_.Pass());
  44   }
  45
  46   // Overridden from base::DiscardableMemory:
  47   bool Lock() override {
  48     DCHECK(!is_locked_);
  49
  50     if (!manager_->LockSpan(span_.get()))
  51       return false;
  52
  53     is_locked_ = true;
  54     return true;
  55   }
  56   void Unlock() override {
  57     DCHECK(is_locked_);
  58
  59     manager_->UnlockSpan(span_.get());
  60     is_locked_ = false;
  61   }
  62   void* Memory() const override {
  63     DCHECK(is_locked_);
  64     return reinterpret_cast<void*>(span_->start() * base::GetPageSize());
  65   }
  66
  67  private:
  68   ChildDiscardableSharedMemoryManager* const manager_;
  69   scoped_ptr<DiscardableSharedMemoryHeap::Span> span_;
  70   bool is_locked_;
  71
  72   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryImpl);
  73 };
  74
  75 void SendDeletedDiscardableSharedMemoryMessage(
  76     scoped_refptr<ThreadSafeSender> sender,
  77     DiscardableSharedMemoryId id) {
  78   sender->Send(new ChildProcessHostMsg_DeletedDiscardableSharedMemory(id));
  79 }
  80
  81 }  // namespace
  82
  83 ChildDiscardableSharedMemoryManager::ChildDiscardableSharedMemoryManager(
  84     ThreadSafeSender* sender)
  85     : heap_(base::GetPageSize()), sender_(sender) {
  86 }
  87
  88 ChildDiscardableSharedMemoryManager::~ChildDiscardableSharedMemoryManager() {
  89   // TODO(reveman): Determine if this DCHECK can be enabled. crbug.com/430533
  90   // DCHECK_EQ(heap_.GetSize(), heap_.GetSizeOfFreeLists());
  91   if (heap_.GetSize())
  92     MemoryUsageChanged(0, 0);
  93 }
  94
  95 scoped_ptr<base::DiscardableMemory>
  96 ChildDiscardableSharedMemoryManager::AllocateLockedDiscardableMemory(
  97     size_t size) {
  98   base::AutoLock lock(lock_);
  99
 100   DCHECK_NE(size, 0u);
 101
 102   UMA_HISTOGRAM_CUSTOM_COUNTS("Memory.DiscardableAllocationSize",
 103                               size / 1024,  // In KB
 104                               1,
 105                               4 * 1024 * 1024,  // 4 GB
 106                               50);
 107
 108   // Round up to multiple of page size.
 109   size_t pages = (size + base::GetPageSize() - 1) / base::GetPageSize();
 110
 111   // Default allocation size in pages.
 112   size_t allocation_pages = kAllocationSize / base::GetPageSize();
 113
 114   size_t slack = 0;
 115   // When searching the free lists, allow a slack between required size and
 116   // free span size that is less or equal to kAllocationSize. This is to
 117   // avoid segments larger then kAllocationSize unless they are a perfect
 118   // fit. The result is that large allocations can be reused without reducing
 119   // the ability to discard memory.
 120   if (pages < allocation_pages)
 121     slack = allocation_pages - pages;
 122
 123   size_t heap_size_prior_to_releasing_purged_memory = heap_.GetSize();
 124   for (;;) {
 125     // Search free lists for suitable span.
 126     scoped_ptr<DiscardableSharedMemoryHeap::Span> free_span =
 127         heap_.SearchFreeLists(pages, slack);
 128     if (!free_span.get())
 129       break;
 130
 131     // Attempt to lock |free_span|. Delete span and search free lists again
 132     // if locking failed.
 133     if (free_span->shared_memory()->Lock(
 134             free_span->start() * base::GetPageSize() -
 135                 reinterpret_cast<size_t>(free_span->shared_memory()->memory()),
 136             free_span->length() * base::GetPageSize()) ==
 137         base::DiscardableSharedMemory::FAILED) {
 138       DCHECK(!free_span->shared_memory()->IsMemoryResident());
 139       // We have to release purged memory before |free_span| can be destroyed.
 140       heap_.ReleasePurgedMemory();
 141       DCHECK(!free_span->shared_memory());
 142       continue;
 143     }
 144
 145     // Memory usage is guaranteed to have changed after having removed
 146     // at least one span from the free lists.
 147     MemoryUsageChanged(heap_.GetSize(), heap_.GetSizeOfFreeLists());
 148
 149     return make_scoped_ptr(new DiscardableMemoryImpl(this, free_span.Pass()));
 150   }
 151
 152   // Release purged memory to free up the address space before we attempt to
 153   // allocate more memory.
 154   heap_.ReleasePurgedMemory();
 155
 156   // Make sure crash keys are up to date in case allocation fails.
 157   if (heap_.GetSize() != heap_size_prior_to_releasing_purged_memory)
 158     MemoryUsageChanged(heap_.GetSize(), heap_.GetSizeOfFreeLists());
 159
 160   size_t pages_to_allocate =
 161       std::max(kAllocationSize / base::GetPageSize(), pages);
 162   size_t allocation_size_in_bytes = pages_to_allocate * base::GetPageSize();
 163
 164   DiscardableSharedMemoryId new_id =
 165       g_next_discardable_shared_memory_id.GetNext();
 166
 167   // Ask parent process to allocate a new discardable shared memory segment.
 168   scoped_ptr<base::DiscardableSharedMemory> shared_memory(
 169       AllocateLockedDiscardableSharedMemory(allocation_size_in_bytes, new_id));
 170
 171   // Create span for allocated memory.
 172   scoped_ptr<DiscardableSharedMemoryHeap::Span> new_span(heap_.Grow(
 173       shared_memory.Pass(), allocation_size_in_bytes,
 174       base::Bind(&SendDeletedDiscardableSharedMemoryMessage, sender_, new_id)));
 175
 176   // Unlock and insert any left over memory into free lists.
 177   if (pages < pages_to_allocate) {
 178     scoped_ptr<DiscardableSharedMemoryHeap::Span> leftover =
 179         heap_.Split(new_span.get(), pages);
 180     leftover->shared_memory()->Unlock(
 181         leftover->start() * base::GetPageSize() -
 182             reinterpret_cast<size_t>(leftover->shared_memory()->memory()),
 183         leftover->length() * base::GetPageSize());
 184     heap_.MergeIntoFreeLists(leftover.Pass());
 185   }
 186
 187   MemoryUsageChanged(heap_.GetSize(), heap_.GetSizeOfFreeLists());
 188
 189   return make_scoped_ptr(new DiscardableMemoryImpl(this, new_span.Pass()));
 190 }
 191
 192 void ChildDiscardableSharedMemoryManager::ReleaseFreeMemory() {
 193   base::AutoLock lock(lock_);
 194
 195   size_t heap_size_prior_to_releasing_memory = heap_.GetSize();
 196
 197   // Release both purged and free memory.
 198   heap_.ReleasePurgedMemory();
 199   heap_.ReleaseFreeMemory();
 200
 201   if (heap_.GetSize() != heap_size_prior_to_releasing_memory)
 202     MemoryUsageChanged(heap_.GetSize(), heap_.GetSizeOfFreeLists());
 203 }
 204
 205 bool ChildDiscardableSharedMemoryManager::LockSpan(
 206     DiscardableSharedMemoryHeap::Span* span) {
 207   base::AutoLock lock(lock_);
 208
 209   if (!span->shared_memory())
 210     return false;
 211
 212   size_t offset = span->start() * base::GetPageSize() -
 213       reinterpret_cast<size_t>(span->shared_memory()->memory());
 214   size_t length = span->length() * base::GetPageSize();
 215
 216   switch (span->shared_memory()->Lock(offset, length)) {
 217     case base::DiscardableSharedMemory::SUCCESS:
 218       return true;
 219     case base::DiscardableSharedMemory::PURGED:
 220       span->shared_memory()->Unlock(offset, length);
 221       return false;
 222     case base::DiscardableSharedMemory::FAILED:
 223       return false;
 224   }
 225
 226   NOTREACHED();
 227   return false;
 228 }
 229
 230 void ChildDiscardableSharedMemoryManager::UnlockSpan(
 231     DiscardableSharedMemoryHeap::Span* span) {
 232   base::AutoLock lock(lock_);
 233
 234   DCHECK(span->shared_memory());
 235   size_t offset = span->start() * base::GetPageSize() -
 236       reinterpret_cast<size_t>(span->shared_memory()->memory());
 237   size_t length = span->length() * base::GetPageSize();
 238
 239   return span->shared_memory()->Unlock(offset, length);
 240 }
 241
 242 void ChildDiscardableSharedMemoryManager::ReleaseSpan(
 243     scoped_ptr<DiscardableSharedMemoryHeap::Span> span) {
 244   base::AutoLock lock(lock_);
 245
 246   // Delete span instead of merging it into free lists if memory is gone.
 247   if (!span->shared_memory())
 248     return;
 249
 250   heap_.MergeIntoFreeLists(span.Pass());
 251
 252   // Bytes of free memory changed.
 253   MemoryUsageChanged(heap_.GetSize(), heap_.GetSizeOfFreeLists());
 254 }
 255
 256 scoped_ptr<base::DiscardableSharedMemory>
 257 ChildDiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
 258     size_t size,
 259     DiscardableSharedMemoryId id) {
 260   TRACE_EVENT2("renderer",
 261                "ChildDiscardableSharedMemoryManager::"
 262                "AllocateLockedDiscardableSharedMemory",
 263                "size", size, "id", id);
 264
 265   base::SharedMemoryHandle handle = base::SharedMemory::NULLHandle();
 266   sender_->Send(
 267       new ChildProcessHostMsg_SyncAllocateLockedDiscardableSharedMemory(
 268           size, id, &handle));
 269   scoped_ptr<base::DiscardableSharedMemory> memory(
 270       new base::DiscardableSharedMemory(handle));
 271   if (!memory->Map(size))
 272     base::TerminateBecauseOutOfMemory(size);
 273   return memory.Pass();
 274 }
 275
 276 void ChildDiscardableSharedMemoryManager::MemoryUsageChanged(
 277     size_t new_bytes_total,
 278     size_t new_bytes_free) const {
 279   TRACE_COUNTER2("renderer", "DiscardableMemoryUsage", "allocated",
 280                  new_bytes_total - new_bytes_free, "free", new_bytes_free);
 281
 282   static const char kDiscardableMemoryAllocatedKey[] =
 283       "discardable-memory-allocated";
 284   base::debug::SetCrashKeyValue(kDiscardableMemoryAllocatedKey,
 285                                 base::Uint64ToString(new_bytes_total));
 286
 287   static const char kDiscardableMemoryFreeKey[] = "discardable-memory-free";
 288   base::debug::SetCrashKeyValue(kDiscardableMemoryFreeKey,
 289                                 base::Uint64ToString(new_bytes_free));
 290 }
 291
 292 }  // namespace content