PartitionAlloc: PCScan: Perform scan only when quarantine is larger than the...

PartitionAlloc: PCScan: Perform scan only when quarantine is larger than the minimum scanning threshold.

This CL also another Reclaim mode to PartitionAllocMemoryReclaimer to force a scan when memory is critical.

Bug: 11297512
Change-Id: I054d8d032ed0b7e3abc9da57b33e6e471c830ed6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2550062
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829663}

base/allocator/partition_allocator/memory_reclaimer.cc

@@ -95,23 +95,34 @@ void PartitionAllocMemoryReclaimer::Start(
   // singleton.
   timer_->Start(
       FROM_HERE, kInterval,
-      BindRepeating(&PartitionAllocMemoryReclaimer::Reclaim, Unretained(this)));
+      BindRepeating(&PartitionAllocMemoryReclaimer::ReclaimPeriodically,
+                    Unretained(this)));
 }
 
 PartitionAllocMemoryReclaimer::PartitionAllocMemoryReclaimer() = default;
 PartitionAllocMemoryReclaimer::~PartitionAllocMemoryReclaimer() = default;
 
-void PartitionAllocMemoryReclaimer::Reclaim() {
-  AutoLock lock(lock_);  // Has to protect from concurrent (Un)Register calls.
-  TRACE_EVENT0("base", "PartitionAllocMemoryReclaimer::Reclaim()");
+void PartitionAllocMemoryReclaimer::ReclaimAll() {
+  constexpr int kFlags = PartitionPurgeDecommitEmptySlotSpans |
+                         PartitionPurgeDiscardUnusedSystemPages |
+                         PartitionPurgeForceAllFreed;
+  Reclaim(kFlags);
+}
 
+void PartitionAllocMemoryReclaimer::ReclaimPeriodically() {
   constexpr int kFlags = PartitionPurgeDecommitEmptySlotSpans |
                          PartitionPurgeDiscardUnusedSystemPages;
+  Reclaim(kFlags);
+}
+
+void PartitionAllocMemoryReclaimer::Reclaim(int flags) {
+  AutoLock lock(lock_);  // Has to protect from concurrent (Un)Register calls.
+  TRACE_EVENT0("base", "PartitionAllocMemoryReclaimer::Reclaim()");
 
   for (auto* partition : thread_safe_partitions_)
-    partition->PurgeMemory(kFlags);
+    partition->PurgeMemory(flags);
   for (auto* partition : thread_unsafe_partitions_)
-    partition->PurgeMemory(kFlags);
+    partition->PurgeMemory(flags);
 }
 
 void PartitionAllocMemoryReclaimer::ResetForTesting() {

base/allocator/partition_allocator/memory_reclaimer.h

@@ -42,12 +42,17 @@ class BASE_EXPORT PartitionAllocMemoryReclaimer {
   void UnregisterPartition(PartitionRoot<internal::NotThreadSafe>* partition);
   // Starts the periodic reclaim. Should be called once.
   void Start(scoped_refptr<SequencedTaskRunner> task_runner);
-  // Triggers an explicit reclaim now.
-  void Reclaim();
+  // Triggers an explicit reclaim now reclaiming all free memory
+  void ReclaimAll();
+  // Triggers an explicit reclaim now to reclaim as much free memory as
+  // possible.
+  void ReclaimPeriodically();
 
  private:
   PartitionAllocMemoryReclaimer();
   ~PartitionAllocMemoryReclaimer();
+  // |flags| is an OR of base::PartitionPurgeFlags
+  void Reclaim(int flags);
   void ReclaimAndReschedule();
   void ResetForTesting();
 

base/allocator/partition_allocator/memory_reclaimer_unittest.cc

@@ -98,7 +98,7 @@ TEST_F(PartitionAllocMemoryReclaimerTest, Reclaim) {
 
     size_t committed_before = root->get_total_size_of_committed_pages();
     EXPECT_GT(committed_before, committed_initially);
-    PartitionAllocMemoryReclaimer::Instance()->Reclaim();
+    PartitionAllocMemoryReclaimer::Instance()->ReclaimAll();
     size_t committed_after = root->get_total_size_of_committed_pages();
 
     EXPECT_LT(committed_after, committed_before);

base/allocator/partition_allocator/partition_root.cc

@@ -620,7 +620,7 @@ void* PartitionRoot<thread_safe>::ReallocFlags(int flags,
 template <bool thread_safe>
 void PartitionRoot<thread_safe>::PurgeMemory(int flags) {
   // TODO(chromium:1129751): Change to LIKELY once PCScan is enabled by default.
-  if (UNLIKELY(pcscan)) {
+  if (UNLIKELY(pcscan) && (flags & PartitionPurgeForceAllFreed)) {
     pcscan->PerformScanIfNeeded(
         internal::PCScan<thread_safe>::InvocationMode::kBlocking);
   }

base/allocator/partition_allocator/partition_root.h

@@ -78,6 +78,8 @@ enum PartitionPurgeFlags {
   // size. It often frees a similar amount of memory to decommitting the empty
   // slot spans, though.
   PartitionPurgeDiscardUnusedSystemPages = 1 << 1,
+  // Free calls which have not been marterialized are forced now.
+  PartitionPurgeForceAllFreed = 1 << 2,
 };
 
 // Options struct used to configure PartitionRoot and PartitionAllocator.

base/allocator/partition_allocator/pcscan.cc

@@ -486,8 +486,7 @@ void PCScan<thread_safe>::PerformScan(InvocationMode invocation_mode) {
 
 template <bool thread_safe>
 void PCScan<thread_safe>::PerformScanIfNeeded(InvocationMode invocation_mode) {
-  // Perform PCScan only if quarantine is not empty.
-  if (quarantine_data_.size())
+  if (quarantine_data_.MinimumScanningThresholdReached())
     PerformScan(invocation_mode);
 }
 

base/allocator/partition_allocator/pcscan.h

@@ -73,6 +73,10 @@ class BASE_EXPORT PCScan final {
     }
     size_t last_size() const { return last_size_; }
 
+    bool MinimumScanningThresholdReached() const {
+      return size() > kQuarantineSizeMinLimit;
+    }
+
    private:
     static constexpr size_t kQuarantineSizeMinLimit = 1 * 1024 * 1024;
 

third_party/blink/renderer/platform/instrumentation/memory_pressure_listener.cc

@@ -29,7 +29,7 @@ namespace blink {
 // Function defined in third_party/blink/public/web/blink.h.
 void DecommitFreeableMemory() {
   CHECK(IsMainThread());
-  base::PartitionAllocMemoryReclaimer::Instance()->Reclaim();
+  base::PartitionAllocMemoryReclaimer::Instance()->ReclaimAll();
 }
 
 // static
@@ -106,7 +106,7 @@ void MemoryPressureListenerRegistry::OnMemoryPressure(
   CHECK(IsMainThread());
   for (auto& client : clients_)
     client->OnMemoryPressure(level);
-  base::PartitionAllocMemoryReclaimer::Instance()->Reclaim();
+  base::PartitionAllocMemoryReclaimer::Instance()->ReclaimAll();
 }
 
 void MemoryPressureListenerRegistry::OnPurgeMemory() {
@@ -114,7 +114,7 @@ void MemoryPressureListenerRegistry::OnPurgeMemory() {
   for (auto& client : clients_)
     client->OnPurgeMemory();
   ImageDecodingStore::Instance().Clear();
-  base::PartitionAllocMemoryReclaimer::Instance()->Reclaim();
+  base::PartitionAllocMemoryReclaimer::Instance()->ReclaimAll();
 
   // Thread-specific data never issues a layout, so we are safe here.
   MutexLocker lock(threads_mutex_);

third_party/blink/renderer/platform/wtf/allocator/partitions_test.cc

@@ -19,7 +19,7 @@ namespace WTF {
 class PartitionsTest : public ::testing::Test {
  protected:
   void TearDown() override {
-    base::PartitionAllocMemoryReclaimer::Instance()->Reclaim();
+    base::PartitionAllocMemoryReclaimer::Instance()->ReclaimAll();
   }
 };
 
@@ -68,7 +68,7 @@ TEST_F(PartitionsTest, Decommit) {
   // Decommit is not triggered by deallocation.
   EXPECT_GT(committed_after, committed_before);
   // Decommit works.
-  base::PartitionAllocMemoryReclaimer::Instance()->Reclaim();
+  base::PartitionAllocMemoryReclaimer::Instance()->ReclaimAll();
   EXPECT_LT(Partitions::TotalSizeOfCommittedPages(), committed_after);
 }