Add the rate of js invocations from the api as a signal of idleness

src/heap/memory-reducer.cc

Index: src/heap/memory-reducer.cc
diff --git a/src/heap/memory-reducer.cc b/src/heap/memory-reducer.cc
index 13aa09daa5fddb932a991fe77b0805d614defcbf..8e144c6caa6c4df103ef4191f25ec2ddba9fb406 100644
--- a/src/heap/memory-reducer.cc
+++ b/src/heap/memory-reducer.cc
@@ -24,15 +24,19 @@ MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
 
 
 void MemoryReducer::TimerTask::RunInternal() {

[Hannes Payer (out of office), 2015/10/28 14:58:08]

Can we leave a comment somewhere mentioning under which conditions the memory
reducer will trigger?

[ulan, 2015/10/29 12:39:24]

Done.

+  const double kJsCallsPerMsThreshold = 0.25;
   Heap* heap = memory_reducer_->heap();
   Event event;
   double time_ms = heap->MonotonicallyIncreasingTimeInMs();
   heap->tracer()->SampleAllocation(time_ms, heap->NewSpaceAllocationCounter(),
                                    heap->OldGenerationAllocationCounter());
+  double js_call_rate = memory_reducer_->SampleAndGetJsCallsPerMs(time_ms);
+  bool is_idle =
+      js_call_rate < kJsCallsPerMsThreshold && heap->HasLowAllocationRate();
   event.type = kTimer;
   event.time_ms = time_ms;
   event.should_start_incremental_gc =
-      heap->HasLowAllocationRate() || heap->ShouldOptimizeForMemoryUsage();
+      is_idle || heap->ShouldOptimizeForMemoryUsage();
   event.can_start_incremental_gc =
       heap->incremental_marking()->IsStopped() &&
       heap->incremental_marking()->CanBeActivated();
@@ -40,6 +44,16 @@ void MemoryReducer::TimerTask::RunInternal() {
 }
 
 
+double MemoryReducer::SampleAndGetJsCallsPerMs(double time_ms) {
+  unsigned int counter = heap()->isolate()->js_calls_from_api_counter();
+  unsigned int call_delta = counter - js_calls_counter_;
+  double time_delta_ms = time_ms - js_calls_sample_time_ms_;
+  js_calls_counter_ = counter;
+  js_calls_sample_time_ms_ = time_ms;
+  return time_delta_ms > 0 ? call_delta / time_delta_ms : 0;
+}
+
+
 void MemoryReducer::NotifyTimer(const Event& event) {
   DCHECK_EQ(kTimer, event.type);
   DCHECK_EQ(kWait, state_.action);
@@ -70,7 +84,7 @@ void MemoryReducer::NotifyTimer(const Event& event) {
           "Memory reducer: finalize incremental marking");
     }
     // Re-schedule the timer.
-    ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
+    ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
     if (FLAG_trace_gc_verbose) {
       PrintIsolate(heap()->isolate(), "Memory reducer: waiting for %.f ms\n",
                    state_.next_gc_start_ms - event.time_ms);
@@ -85,7 +99,7 @@ void MemoryReducer::NotifyMarkCompact(const Event& event) {
   state_ = Step(state_, event);
   if (old_action != kWait && state_.action == kWait) {
     // If we are transitioning to the WAIT state, start the timer.
-    ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
+    ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
   }
   if (old_action == kRun) {
     if (FLAG_trace_gc_verbose) {
@@ -103,7 +117,7 @@ void MemoryReducer::NotifyContextDisposed(const Event& event) {
   state_ = Step(state_, event);
   if (old_action != kWait && state_.action == kWait) {
     // If we are transitioning to the WAIT state, start the timer.
-    ScheduleTimer(state_.next_gc_start_ms - event.time_ms);
+    ScheduleTimer(event.time_ms, state_.next_gc_start_ms - event.time_ms);
   }
 }
 
@@ -172,8 +186,10 @@ MemoryReducer::State MemoryReducer::Step(const State& state,
 }
 
 
-void MemoryReducer::ScheduleTimer(double delay_ms) {
+void MemoryReducer::ScheduleTimer(double time_ms, double delay_ms) {
   DCHECK(delay_ms > 0);
+  // Record the time and the js call counter.
+  SampleAndGetJsCallsPerMs(time_ms);
   // Leave some room for precision error in task scheduler.
   const double kSlackMs = 100;
   v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap()->isolate());