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

src/heap/memory-reducer.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/memory-reducer.h"
 
 #include "src/flags.h"
 #include "src/heap/gc-tracer.h"
 #include "src/heap/heap-inl.h"
 #include "src/utils.h"
 #include "src/v8.h"
 
 namespace v8 {
 namespace internal {
 
 const int MemoryReducer::kLongDelayMs = 20000;
 const int MemoryReducer::kShortDelayMs = 500;
 const int MemoryReducer::kWatchdogDelayMs = 100000;
 const int MemoryReducer::kMaxNumberOfGCs = 3;
 
 MemoryReducer::TimerTask::TimerTask(MemoryReducer* memory_reducer)
     : CancelableTask(memory_reducer->heap()->isolate()),
       memory_reducer_(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();
   memory_reducer_->NotifyTimer(event);
 }
 
 
+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);
   state_ = Step(state_, event);
   if (state_.action == kRun) {
     DCHECK(heap()->incremental_marking()->IsStopped());
     DCHECK(FLAG_incremental_marking);
     if (FLAG_trace_gc_verbose) {
       PrintIsolate(heap()->isolate(), "Memory reducer: started GC #%d\n",
                    state_.started_gcs);
@@ skipping 10 matching lines @@
                         kIncrementalMarkingDelayMs;
       heap()->incremental_marking()->AdvanceIncrementalMarking(
           0, deadline, i::IncrementalMarking::StepActions(
                            i::IncrementalMarking::NO_GC_VIA_STACK_GUARD,
                            i::IncrementalMarking::FORCE_MARKING,
                            i::IncrementalMarking::FORCE_COMPLETION));
       heap()->FinalizeIncrementalMarkingIfComplete(
           "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);
     }
   }
 }
 
 
 void MemoryReducer::NotifyMarkCompact(const Event& event) {
   DCHECK_EQ(kMarkCompact, event.type);
   Action old_action = state_.action;
   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) {
       PrintIsolate(heap()->isolate(), "Memory reducer: finished GC #%d (%s)\n",
                    state_.started_gcs,
                    state_.action == kWait ? "will do more" : "done");
     }
   }
 }
 
 
 void MemoryReducer::NotifyContextDisposed(const Event& event) {
   DCHECK_EQ(kContextDisposed, event.type);
   Action old_action = state_.action;
   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);
   }
 }
 
 
 bool MemoryReducer::WatchdogGC(const State& state, const Event& event) {
   return state.last_gc_time_ms != 0 &&
          event.time_ms > state.last_gc_time_ms + kWatchdogDelayMs;
 }
 
 
@@ skipping 48 matching lines @@
         } else {
           return State(kDone, kMaxNumberOfGCs, 0.0, event.time_ms);
         }
       }
   }
   UNREACHABLE();
   return State(kDone, 0, 0, 0.0);  // Make the compiler happy.
 }
 
 
-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());
   auto timer_task = new MemoryReducer::TimerTask(this);
   V8::GetCurrentPlatform()->CallDelayedOnForegroundThread(
       isolate, timer_task, (delay_ms + kSlackMs) / 1000.0);
 }
 
 
 void MemoryReducer::TearDown() { state_ = State(kDone, 0, 0, 0.0); }
 
 }  // namespace internal
 }  // namespace v8