content/common/host_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/common/host_discardable_shared_memory_manager.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/atomic_sequence_num.h"
  10 #include "base/bind.h"
  11 #include "base/callback.h"
  12 #include "base/debug/crash_logging.h"
  13 #include "base/lazy_instance.h"
  14 #include "base/memory/discardable_memory.h"
  15 #include "base/numerics/safe_math.h"
  16 #include "base/strings/string_number_conversions.h"
  17 #include "base/sys_info.h"
  18 #include "base/trace_event/trace_event.h"
  19
  20 namespace content {
  21 namespace {
  22
  23 class DiscardableMemoryImpl : public base::DiscardableMemory {
  24  public:
  25   DiscardableMemoryImpl(scoped_ptr<base::DiscardableSharedMemory> shared_memory,
  26                         const base::Closure& deleted_callback)
  27       : shared_memory_(shared_memory.Pass()),
  28         deleted_callback_(deleted_callback),
  29         is_locked_(true) {}
  30
  31   ~DiscardableMemoryImpl() override {
  32     if (is_locked_)
  33       shared_memory_->Unlock(0, 0);
  34
  35     deleted_callback_.Run();
  36   }
  37
  38   // Overridden from base::DiscardableMemory:
  39   bool Lock() override {
  40     DCHECK(!is_locked_);
  41
  42     if (shared_memory_->Lock(0, 0) != base::DiscardableSharedMemory::SUCCESS)
  43       return false;
  44
  45     is_locked_ = true;
  46     return true;
  47   }
  48   void Unlock() override {
  49     DCHECK(is_locked_);
  50
  51     shared_memory_->Unlock(0, 0);
  52     is_locked_ = false;
  53   }
  54   void* Memory() const override {
  55     DCHECK(is_locked_);
  56     return shared_memory_->memory();
  57   }
  58
  59  private:
  60   scoped_ptr<base::DiscardableSharedMemory> shared_memory_;
  61   const base::Closure deleted_callback_;
  62   bool is_locked_;
  63
  64   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryImpl);
  65 };
  66
  67 base::LazyInstance<HostDiscardableSharedMemoryManager>
  68     g_discardable_shared_memory_manager = LAZY_INSTANCE_INITIALIZER;
  69
  70 const int64_t kMaxDefaultMemoryLimit = 512 * 1024 * 1024;
  71
  72 const int kEnforceMemoryPolicyDelayMs = 1000;
  73
  74 // Global atomic to generate unique discardable shared memory IDs.
  75 base::StaticAtomicSequenceNumber g_next_discardable_shared_memory_id;
  76
  77 }  // namespace
  78
  79 HostDiscardableSharedMemoryManager::MemorySegment::MemorySegment(
  80     scoped_ptr<base::DiscardableSharedMemory> memory)
  81     : memory_(memory.Pass()) {
  82 }
  83
  84 HostDiscardableSharedMemoryManager::MemorySegment::~MemorySegment() {
  85 }
  86
  87 HostDiscardableSharedMemoryManager::HostDiscardableSharedMemoryManager()
  88     : memory_limit_(
  89           // Allow 25% of physical memory to be used for discardable memory.
  90           std::min(base::SysInfo::AmountOfPhysicalMemory() / 4,
  91                    kMaxDefaultMemoryLimit)),
  92       bytes_allocated_(0),
  93       memory_pressure_listener_(new base::MemoryPressureListener(
  94           base::Bind(&HostDiscardableSharedMemoryManager::OnMemoryPressure,
  95                      base::Unretained(this)))),
  96       enforce_memory_policy_pending_(false),
  97       weak_ptr_factory_(this) {
  98   DCHECK_NE(memory_limit_, 0u);
  99 }
 100
 101 HostDiscardableSharedMemoryManager::~HostDiscardableSharedMemoryManager() {
 102 }
 103
 104 HostDiscardableSharedMemoryManager*
 105 HostDiscardableSharedMemoryManager::current() {
 106   return g_discardable_shared_memory_manager.Pointer();
 107 }
 108
 109 scoped_ptr<base::DiscardableMemory>
 110 HostDiscardableSharedMemoryManager::AllocateLockedDiscardableMemory(
 111     size_t size) {
 112   DiscardableSharedMemoryId new_id =
 113       g_next_discardable_shared_memory_id.GetNext();
 114   base::ProcessHandle current_process_handle = base::GetCurrentProcessHandle();
 115
 116   // Note: Use DiscardableSharedMemoryHeap for in-process allocation
 117   // of discardable memory if the cost of each allocation is too high.
 118   base::SharedMemoryHandle handle;
 119   AllocateLockedDiscardableSharedMemory(current_process_handle, size, new_id,
 120                                         &handle);
 121   CHECK(base::SharedMemory::IsHandleValid(handle));
 122   scoped_ptr<base::DiscardableSharedMemory> memory(
 123       new base::DiscardableSharedMemory(handle));
 124   CHECK(memory->Map(size));
 125   return make_scoped_ptr(new DiscardableMemoryImpl(
 126       memory.Pass(),
 127       base::Bind(
 128           &HostDiscardableSharedMemoryManager::DeletedDiscardableSharedMemory,
 129           base::Unretained(this), new_id, current_process_handle)));
 130 }
 131
 132 void HostDiscardableSharedMemoryManager::
 133     AllocateLockedDiscardableSharedMemoryForChild(
 134         base::ProcessHandle process_handle,
 135         size_t size,
 136         DiscardableSharedMemoryId id,
 137         base::SharedMemoryHandle* shared_memory_handle) {
 138   AllocateLockedDiscardableSharedMemory(process_handle, size, id,
 139                                         shared_memory_handle);
 140 }
 141
 142 void HostDiscardableSharedMemoryManager::ChildDeletedDiscardableSharedMemory(
 143     DiscardableSharedMemoryId id,
 144     base::ProcessHandle process_handle) {
 145   DeletedDiscardableSharedMemory(id, process_handle);
 146 }
 147
 148 void HostDiscardableSharedMemoryManager::ProcessRemoved(
 149     base::ProcessHandle process_handle) {
 150   base::AutoLock lock(lock_);
 151
 152   ProcessMap::iterator process_it = processes_.find(process_handle);
 153   if (process_it == processes_.end())
 154     return;
 155
 156   size_t bytes_allocated_before_releasing_memory = bytes_allocated_;
 157
 158   for (auto& segment_it : process_it->second)
 159     ReleaseMemory(segment_it.second->memory());
 160
 161   processes_.erase(process_it);
 162
 163   if (bytes_allocated_ != bytes_allocated_before_releasing_memory)
 164     BytesAllocatedChanged(bytes_allocated_);
 165 }
 166
 167 void HostDiscardableSharedMemoryManager::SetMemoryLimit(size_t limit) {
 168   base::AutoLock lock(lock_);
 169
 170   memory_limit_ = limit;
 171   ReduceMemoryUsageUntilWithinMemoryLimit();
 172 }
 173
 174 void HostDiscardableSharedMemoryManager::EnforceMemoryPolicy() {
 175   base::AutoLock lock(lock_);
 176
 177   enforce_memory_policy_pending_ = false;
 178   ReduceMemoryUsageUntilWithinMemoryLimit();
 179 }
 180
 181 size_t HostDiscardableSharedMemoryManager::GetBytesAllocated() {
 182   base::AutoLock lock(lock_);
 183
 184   return bytes_allocated_;
 185 }
 186
 187 void HostDiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
 188     base::ProcessHandle process_handle,
 189     size_t size,
 190     DiscardableSharedMemoryId id,
 191     base::SharedMemoryHandle* shared_memory_handle) {
 192   base::AutoLock lock(lock_);
 193
 194   // Make sure |id| is not already in use.
 195   MemorySegmentMap& process_segments = processes_[process_handle];
 196   if (process_segments.find(id) != process_segments.end()) {
 197     LOG(ERROR) << "Invalid discardable shared memory ID";
 198     *shared_memory_handle = base::SharedMemory::NULLHandle();
 199     return;
 200   }
 201
 202   // Memory usage must be reduced to prevent the addition of |size| from
 203   // taking usage above the limit. Usage should be reduced to 0 in cases
 204   // where |size| is greater than the limit.
 205   size_t limit = 0;
 206   // Note: the actual mapped size can be larger than requested and cause
 207   // |bytes_allocated_| to temporarily be larger than |memory_limit_|. The
 208   // error is minimized by incrementing |bytes_allocated_| with the actual
 209   // mapped size rather than |size| below.
 210   if (size < memory_limit_)
 211     limit = memory_limit_ - size;
 212
 213   if (bytes_allocated_ > limit)
 214     ReduceMemoryUsageUntilWithinLimit(limit);
 215
 216   scoped_ptr<base::DiscardableSharedMemory> memory(
 217       new base::DiscardableSharedMemory);
 218   if (!memory->CreateAndMap(size)) {
 219     *shared_memory_handle = base::SharedMemory::NULLHandle();
 220     return;
 221   }
 222
 223   if (!memory->ShareToProcess(process_handle, shared_memory_handle)) {
 224     LOG(ERROR) << "Cannot share discardable memory segment";
 225     *shared_memory_handle = base::SharedMemory::NULLHandle();
 226     return;
 227   }
 228
 229   base::CheckedNumeric<size_t> checked_bytes_allocated = bytes_allocated_;
 230   checked_bytes_allocated += memory->mapped_size();
 231   if (!checked_bytes_allocated.IsValid()) {
 232     *shared_memory_handle = base::SharedMemory::NULLHandle();
 233     return;
 234   }
 235
 236   bytes_allocated_ = checked_bytes_allocated.ValueOrDie();
 237   BytesAllocatedChanged(bytes_allocated_);
 238
 239   scoped_refptr<MemorySegment> segment(new MemorySegment(memory.Pass()));
 240   process_segments[id] = segment.get();
 241   segments_.push_back(segment.get());
 242   std::push_heap(segments_.begin(), segments_.end(), CompareMemoryUsageTime);
 243
 244   if (bytes_allocated_ > memory_limit_)
 245     ScheduleEnforceMemoryPolicy();
 246 }
 247
 248 void HostDiscardableSharedMemoryManager::DeletedDiscardableSharedMemory(
 249     DiscardableSharedMemoryId id,
 250     base::ProcessHandle process_handle) {
 251   base::AutoLock lock(lock_);
 252
 253   MemorySegmentMap& process_segments = processes_[process_handle];
 254
 255   MemorySegmentMap::iterator segment_it = process_segments.find(id);
 256   if (segment_it == process_segments.end()) {
 257     LOG(ERROR) << "Invalid discardable shared memory ID";
 258     return;
 259   }
 260
 261   size_t bytes_allocated_before_releasing_memory = bytes_allocated_;
 262
 263   ReleaseMemory(segment_it->second->memory());
 264
 265   process_segments.erase(segment_it);
 266
 267   if (bytes_allocated_ != bytes_allocated_before_releasing_memory)
 268     BytesAllocatedChanged(bytes_allocated_);
 269 }
 270
 271 void HostDiscardableSharedMemoryManager::OnMemoryPressure(
 272     base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
 273   base::AutoLock lock(lock_);
 274
 275   switch (memory_pressure_level) {
 276     case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE:
 277       break;
 278     case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE:
 279       // Purge memory until usage is within half of |memory_limit_|.
 280       ReduceMemoryUsageUntilWithinLimit(memory_limit_ / 2);
 281       break;
 282     case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL:
 283       // Purge everything possible when pressure is critical.
 284       ReduceMemoryUsageUntilWithinLimit(0);
 285       break;
 286   }
 287 }
 288
 289 void
 290 HostDiscardableSharedMemoryManager::ReduceMemoryUsageUntilWithinMemoryLimit() {
 291   lock_.AssertAcquired();
 292
 293   if (bytes_allocated_ <= memory_limit_)
 294     return;
 295
 296   ReduceMemoryUsageUntilWithinLimit(memory_limit_);
 297   if (bytes_allocated_ > memory_limit_)
 298     ScheduleEnforceMemoryPolicy();
 299 }
 300
 301 void HostDiscardableSharedMemoryManager::ReduceMemoryUsageUntilWithinLimit(
 302     size_t limit) {
 303   TRACE_EVENT1("renderer_host",
 304                "HostDiscardableSharedMemoryManager::"
 305                "ReduceMemoryUsageUntilWithinLimit",
 306                "bytes_allocated",
 307                bytes_allocated_);
 308
 309   // Usage time of currently locked segments are updated to this time and
 310   // we stop eviction attempts as soon as we come across a segment that we've
 311   // previously tried to evict but was locked.
 312   base::Time current_time = Now();
 313
 314   lock_.AssertAcquired();
 315   size_t bytes_allocated_before_purging = bytes_allocated_;
 316   while (!segments_.empty()) {
 317     if (bytes_allocated_ <= limit)
 318       break;
 319
 320     // Stop eviction attempts when the LRU segment is currently in use.
 321     if (segments_.front()->memory()->last_known_usage() >= current_time)
 322       break;
 323
 324     std::pop_heap(segments_.begin(), segments_.end(), CompareMemoryUsageTime);
 325     scoped_refptr<MemorySegment> segment = segments_.back();
 326     segments_.pop_back();
 327
 328     // Attempt to purge LRU segment. When successful, released the memory.
 329     if (segment->memory()->Purge(current_time)) {
 330 #if defined(DISCARDABLE_SHARED_MEMORY_SHRINKING)
 331       size_t size = segment->memory()->mapped_size();
 332       DCHECK_GE(bytes_allocated_, size);
 333       bytes_allocated_ -= size;
 334       // Shrink memory segment. This will immediately release the memory to
 335       // the OS.
 336       segment->memory()->Shrink();
 337       DCHECK_EQ(segment->memory()->mapped_size(), 0u);
 338 #endif
 339       ReleaseMemory(segment->memory());
 340       continue;
 341     }
 342
 343     // Add memory segment (with updated usage timestamp) back on heap after
 344     // failed attempt to purge it.
 345     segments_.push_back(segment.get());
 346     std::push_heap(segments_.begin(), segments_.end(), CompareMemoryUsageTime);
 347   }
 348
 349   if (bytes_allocated_ != bytes_allocated_before_purging)
 350     BytesAllocatedChanged(bytes_allocated_);
 351 }
 352
 353 void HostDiscardableSharedMemoryManager::ReleaseMemory(
 354     base::DiscardableSharedMemory* memory) {
 355   lock_.AssertAcquired();
 356
 357   size_t size = memory->mapped_size();
 358   DCHECK_GE(bytes_allocated_, size);
 359   bytes_allocated_ -= size;
 360
 361   // This will unmap the memory segment and drop our reference. The result
 362   // is that the memory will be released to the OS if the child process is
 363   // no longer referencing it.
 364   // Note: We intentionally leave the segment in the |segments| vector to
 365   // avoid reconstructing the heap. The element will be removed from the heap
 366   // when its last usage time is older than all other segments.
 367   memory->Close();
 368 }
 369
 370 void HostDiscardableSharedMemoryManager::BytesAllocatedChanged(
 371     size_t new_bytes_allocated) const {
 372   TRACE_COUNTER1("renderer_host", "TotalDiscardableMemoryUsage",
 373                  new_bytes_allocated);
 374
 375   static const char kTotalDiscardableMemoryAllocatedKey[] =
 376       "total-discardable-memory-allocated";
 377   base::debug::SetCrashKeyValue(kTotalDiscardableMemoryAllocatedKey,
 378                                 base::Uint64ToString(new_bytes_allocated));
 379 }
 380
 381 base::Time HostDiscardableSharedMemoryManager::Now() const {
 382   return base::Time::Now();
 383 }
 384
 385 void HostDiscardableSharedMemoryManager::ScheduleEnforceMemoryPolicy() {
 386   lock_.AssertAcquired();
 387
 388   if (enforce_memory_policy_pending_)
 389     return;
 390
 391   enforce_memory_policy_pending_ = true;
 392   base::MessageLoop::current()->PostDelayedTask(
 393       FROM_HERE,
 394       base::Bind(&HostDiscardableSharedMemoryManager::EnforceMemoryPolicy,
 395                  weak_ptr_factory_.GetWeakPtr()),
 396       base::TimeDelta::FromMilliseconds(kEnforceMemoryPolicyDelayMs));
 397 }
 398
 399 }  // namespace content