Start incremental marking in long idle notification for background tab

disregarding the allocation throughput.

BUG=chromium:506132
LOG=NO

Review URL: https://codereview.chromium.org/1213313004

Cr-Commit-Position: refs/heads/master@{#29515}

src/heap/heap.cc

@@ -4956,6 +4956,19 @@ void Heap::IdleNotificationEpilogue(GCIdleTimeAction action,
 }
 
 
+void Heap::CheckAndNotifyBackgroundIdleNotification(double idle_time_in_ms,
+                                                    double now_ms) {
+  if (idle_time_in_ms >= GCIdleTimeHandler::kMinBackgroundIdleTime) {
+    MemoryReducer::Event event;
+    event.type = MemoryReducer::kBackgroundIdleNotification;
+    event.time_ms = now_ms;
+    event.can_start_incremental_gc = incremental_marking()->IsStopped() &&
+                                     incremental_marking()->CanBeActivated();
+    memory_reducer_.NotifyBackgroundIdleNotification(event);
+  }
+}
+
+
 double Heap::MonotonicallyIncreasingTimeInMs() {
   return V8::GetCurrentPlatform()->MonotonicallyIncreasingTime() *
          static_cast<double>(base::Time::kMillisecondsPerSecond);
@@ -4980,6 +4993,8 @@ bool Heap::IdleNotification(double deadline_in_seconds) {
   double start_ms = MonotonicallyIncreasingTimeInMs();
   double idle_time_in_ms = deadline_in_ms - start_ms;
 
+  CheckAndNotifyBackgroundIdleNotification(idle_time_in_ms, start_ms);
+
   tracer()->SampleAllocation(start_ms, NewSpaceAllocationCounter(),
                              OldGenerationAllocationCounter());
 

src/heap/heap.h

@@ -2279,6 +2279,8 @@ class Heap {
   void IdleNotificationEpilogue(GCIdleTimeAction action,
                                 GCIdleTimeHandler::HeapState heap_state,
                                 double start_ms, double deadline_in_ms);
+  void CheckAndNotifyBackgroundIdleNotification(double idle_time_in_ms,
+                                                double now_ms);
 
   void ClearObjectStats(bool clear_last_time_stats = false);
 

src/heap/memory-reducer.cc

@@ -82,6 +82,26 @@ void MemoryReducer::NotifyContextDisposed(const Event& event) {
 }
 
 
+void MemoryReducer::NotifyBackgroundIdleNotification(const Event& event) {
+  DCHECK_EQ(kBackgroundIdleNotification, event.type);
+  Action old_action = state_.action;
+  int old_started_gcs = state_.started_gcs;
+  state_ = Step(state_, event);
+  if (old_action == kWait && state_.action == kWait &&
+      old_started_gcs + 1 == state_.started_gcs) {
+    DCHECK(heap()->incremental_marking()->IsStopped());
+    DCHECK(FLAG_incremental_marking);
+    heap()->StartIdleIncrementalMarking();
+    if (FLAG_trace_gc_verbose) {
+      PrintIsolate(heap()->isolate(),
+                   "Memory reducer: started GC #%d"
+                   " (background idle)\n",
+                   state_.started_gcs);
+    }
+  }
+}
+
+
 // For specification of this function see the comment for MemoryReducer class.
 MemoryReducer::State MemoryReducer::Step(const State& state,
                                          const Event& event) {
@@ -90,16 +110,20 @@ MemoryReducer::State MemoryReducer::Step(const State& state,
   }
   switch (state.action) {
     case kDone:
-      if (event.type == kTimer) {
+      if (event.type == kTimer || event.type == kBackgroundIdleNotification) {
         return state;
       } else {
         DCHECK(event.type == kContextDisposed || event.type == kMarkCompact);
         return State(kWait, 0, event.time_ms + kLongDelayMs);
       }
     case kWait:
-      if (event.type == kContextDisposed) {
+      switch (event.type) {
+        case kContextDisposed:
           return state;
-      } else if (event.type == kTimer && event.can_start_incremental_gc &&
+        case kTimer:
+          if (state.started_gcs >= kMaxNumberOfGCs) {
+            return State(kDone, 0, 0.0);
+          } else if (event.can_start_incremental_gc &&
                      event.low_allocation_rate) {
             if (state.next_gc_start_ms <= event.time_ms) {
               return State(kRun, state.started_gcs + 1, 0.0);
@@ -107,6 +131,18 @@ MemoryReducer::State MemoryReducer::Step(const State& state,
               return state;
             }
           } else {
+            return State(kWait, state.started_gcs,
+                         event.time_ms + kLongDelayMs);
+          }
+        case kBackgroundIdleNotification:
+          if (event.can_start_incremental_gc &&
+              state.started_gcs < kMaxNumberOfGCs) {
+            return State(kWait, state.started_gcs + 1,
+                         event.time_ms + kLongDelayMs);
+          } else {
+            return state;
+          }
+        case kMarkCompact:
           return State(kWait, state.started_gcs, event.time_ms + kLongDelayMs);
       }
     case kRun:

src/heap/memory-reducer.h

@@ -48,6 +48,15 @@ class Heap;
 //     - in the timer callback if the mutator allocation rate is high or
 //       incremental GC is in progress.
 //
+// WAIT n x -> WAIT (n+1) happens:
+//     - on background idle notification, which signals that we can start
+//       incremental marking even if the allocation rate is high.
+// The MemoryReducer starts incremental marking on this transition but still
+// has a pending timer task.
+//
+// WAIT n x -> DONE happens:
+//     - in the timer callback if n >= kMaxNumberOfGCs.
+//
 // WAIT n x -> RUN (n+1) happens:
 //     - in the timer callback if the mutator allocation rate is low
 //       and now_ms >= x and there is no incremental GC in progress.
@@ -81,6 +90,7 @@ class MemoryReducer {
     kTimer,
     kMarkCompact,
     kContextDisposed,
+    kBackgroundIdleNotification
   };
 
   struct Event {
@@ -95,8 +105,8 @@ class MemoryReducer {
   // Callbacks.
   void NotifyTimer(const Event& event);
   void NotifyMarkCompact(const Event& event);
-  void NotifyScavenge(const Event& event);
   void NotifyContextDisposed(const Event& event);
+  void NotifyBackgroundIdleNotification(const Event& event);
   // The step function that computes the next state from the current state and
   // the incoming event.
   static State Step(const State& state, const Event& event);

test/unittests/heap/memory-reducer-unittest.cc

@@ -82,6 +82,16 @@ MemoryReducer::Event ContextDisposedEvent(double time_ms) {
 }
 
 
+MemoryReducer::Event BackgroundIdleNotificationEvent(
+    double time_ms, bool can_start_incremental_gc = true) {
+  MemoryReducer::Event event;
+  event.type = MemoryReducer::kBackgroundIdleNotification;
+  event.time_ms = time_ms;
+  event.can_start_incremental_gc = can_start_incremental_gc;
+  return event;
+}
+
+
 TEST(MemoryReducer, FromDoneToDone) {
   MemoryReducer::State state0(DoneState()), state1(DoneState());
 
@@ -93,6 +103,9 @@ TEST(MemoryReducer, FromDoneToDone) {
 
   state1 = MemoryReducer::Step(state0, TimerEventPendingGC(0));
   EXPECT_EQ(MemoryReducer::kDone, state1.action);
+
+  state1 = MemoryReducer::Step(state0, BackgroundIdleNotificationEvent(0));
+  EXPECT_EQ(MemoryReducer::kDone, state1.action);
 }
 
 
@@ -153,6 +166,23 @@ TEST(MemoryReducer, FromWaitToWait) {
   EXPECT_EQ(MemoryReducer::kWait, state1.action);
   EXPECT_EQ(2000 + MemoryReducer::kLongDelayMs, state1.next_gc_start_ms);
   EXPECT_EQ(state0.started_gcs, state1.started_gcs);
+
+  state1 = MemoryReducer::Step(state0, BackgroundIdleNotificationEvent(2000));
+  EXPECT_EQ(MemoryReducer::kWait, state1.action);
+  EXPECT_EQ(2000 + MemoryReducer::kLongDelayMs, state1.next_gc_start_ms);
+  EXPECT_EQ(state0.started_gcs + 1, state1.started_gcs);
+
+  state1 =
+      MemoryReducer::Step(state0, BackgroundIdleNotificationEvent(2000, false));
+  EXPECT_EQ(MemoryReducer::kWait, state1.action);
+  EXPECT_EQ(state0.next_gc_start_ms, state1.next_gc_start_ms);
+  EXPECT_EQ(state0.started_gcs, state1.started_gcs);
+
+  state0.started_gcs = MemoryReducer::kMaxNumberOfGCs;
+  state1 = MemoryReducer::Step(state0, BackgroundIdleNotificationEvent(2000));
+  EXPECT_EQ(MemoryReducer::kWait, state1.action);
+  EXPECT_EQ(state0.next_gc_start_ms, state1.next_gc_start_ms);
+  EXPECT_EQ(state0.started_gcs, state1.started_gcs);
 }
 
 
@@ -169,6 +199,30 @@ TEST(MemoryReducer, FromWaitToRun) {
 }
 
 
+TEST(MemoryReducer, FromWaitToDone) {
+  if (!FLAG_incremental_marking) return;
+
+  MemoryReducer::State state0(WaitState(2, 0.0)), state1(DoneState());
+
+  state0.started_gcs = MemoryReducer::kMaxNumberOfGCs;
+
+  state1 = MemoryReducer::Step(state0, TimerEventLowAllocationRate(2000));
+  EXPECT_EQ(MemoryReducer::kDone, state1.action);
+  EXPECT_EQ(0, state1.next_gc_start_ms);
+  EXPECT_EQ(0, state1.started_gcs);
+
+  state1 = MemoryReducer::Step(state0, TimerEventHighAllocationRate(2000));
+  EXPECT_EQ(MemoryReducer::kDone, state1.action);
+  EXPECT_EQ(0, state1.next_gc_start_ms);
+  EXPECT_EQ(0, state1.started_gcs);
+
+  state1 = MemoryReducer::Step(state0, TimerEventPendingGC(2000));
+  EXPECT_EQ(MemoryReducer::kDone, state1.action);
+  EXPECT_EQ(0, state1.next_gc_start_ms);
+  EXPECT_EQ(0, state1.started_gcs);
+}
+
+
 TEST(MemoryReducer, FromRunToRun) {
   if (!FLAG_incremental_marking) return;