Take freed handles into account when scheduling idle GCs.

BUG=

Review URL: https://codereview.chromium.org/1145103002

Cr-Commit-Position: refs/heads/master@{#28508}

src/heap/gc-idle-time-handler.cc

@@ -399,7 +399,8 @@ GCIdleTimeHandler::Mode GCIdleTimeHandler::NextMode(
       }
       break;
     case kReduceMemory:
-      if (idle_mark_compacts_ >= kMaxIdleMarkCompacts) {
+      if (idle_mark_compacts_ >= kMaxIdleMarkCompacts ||
+          (idle_mark_compacts_ > 0 && !next_gc_likely_to_collect_more_)) {
         return kDone;
       }
       if (mutator_gcs > idle_mark_compacts_) {

src/heap/gc-idle-time-handler.h

@@ -197,13 +197,17 @@ class GCIdleTimeHandler {
         long_idle_notifications_(0),
         background_idle_notifications_(0),
         idle_times_which_made_no_progress_per_mode_(0),
+        next_gc_likely_to_collect_more_(false),
         mode_(kReduceLatency) {}
 
   GCIdleTimeAction Compute(double idle_time_in_ms, HeapState heap_state);
 
   void NotifyIdleMarkCompact() { ++idle_mark_compacts_; }
 
-  void NotifyMarkCompact() { ++mark_compacts_; }
+  void NotifyMarkCompact(bool next_gc_likely_to_collect_more) {
+    next_gc_likely_to_collect_more_ = next_gc_likely_to_collect_more;
+    ++mark_compacts_;
+  }
 
   void NotifyScavenge() { ++scavenges_; }
 
@@ -261,6 +265,8 @@ class GCIdleTimeHandler {
   // Idle notifications with no progress in the current mode.
   int idle_times_which_made_no_progress_per_mode_;
 
+  bool next_gc_likely_to_collect_more_;
+
   Mode mode_;
 
   DISALLOW_COPY_AND_ASSIGN(GCIdleTimeHandler);

src/heap/heap.cc

@@ -932,7 +932,7 @@ bool Heap::CollectGarbage(GarbageCollector collector, const char* gc_reason,
     }
 
     if (collector == MARK_COMPACTOR) {
-      gc_idle_time_handler_.NotifyMarkCompact();
+      gc_idle_time_handler_.NotifyMarkCompact(next_gc_likely_to_collect_more);
     } else {
       gc_idle_time_handler_.NotifyScavenge();
     }

test/unittests/heap/gc-idle-time-handler-unittest.cc

@@ -67,7 +67,7 @@ class GCIdleTimeHandlerTest : public ::testing::Test {
       GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
       EXPECT_EQ(expected, action.type);
       EXPECT_TRUE(action.reduce_memory);
-      handler()->NotifyMarkCompact();
+      handler()->NotifyMarkCompact(true);
       handler()->NotifyIdleMarkCompact();
     }
     handler()->Compute(idle_time_ms, heap_state);
@@ -82,7 +82,7 @@ class GCIdleTimeHandlerTest : public ::testing::Test {
     for (int i = 0; i < limit; i++) {
       GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
       EXPECT_EQ(DONE, action.type);
-      handler()->NotifyMarkCompact();
+      handler()->NotifyMarkCompact(true);
     }
     handler()->Compute(idle_time_ms, heap_state);
     EXPECT_EQ(GCIdleTimeHandler::kReduceLatency, handler()->mode());
@@ -462,7 +462,7 @@ TEST_F(GCIdleTimeHandlerTest, StopEventually1) {
   for (int i = 0; i < kMaxNotifications && !stopped; i++) {
     GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
     if (action.type == DO_INCREMENTAL_MARKING || action.type == DO_FULL_GC) {
-      handler()->NotifyMarkCompact();
+      handler()->NotifyMarkCompact(true);
       handler()->NotifyIdleMarkCompact();
     }
     if (action.type == DONE) stopped = true;
@@ -579,7 +579,7 @@ TEST_F(GCIdleTimeHandlerTest, StayInReduceLatencyModeBecauseOfMarkCompacts) {
   for (int i = 0; i < kMaxNotifications; i++) {
     GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
     EXPECT_TRUE(DO_NOTHING == action.type || DONE == action.type);
-    if ((i + 1) % limit == 0) handler()->NotifyMarkCompact();
+    if ((i + 1) % limit == 0) handler()->NotifyMarkCompact(true);
     EXPECT_EQ(GCIdleTimeHandler::kReduceLatency, handler()->mode());
   }
 }
@@ -604,7 +604,7 @@ TEST_F(GCIdleTimeHandlerTest, ReduceMemoryToReduceLatency) {
       // ReduceMemory mode should tolerate one mutator GC per idle GC.
       handler()->NotifyScavenge();
       // Notify idle GC.
-      handler()->NotifyMarkCompact();
+      handler()->NotifyMarkCompact(true);
       handler()->NotifyIdleMarkCompact();
     }
     // Transition to ReduceLatency mode after doing |idle_gc| idle GCs.
@@ -635,7 +635,7 @@ TEST_F(GCIdleTimeHandlerTest, ReduceMemoryToDone) {
     // ReduceMemory mode should tolerate one mutator GC per idle GC.
     handler()->NotifyScavenge();
     // Notify idle GC.
-    handler()->NotifyMarkCompact();
+    handler()->NotifyMarkCompact(true);
     handler()->NotifyIdleMarkCompact();
   }
   action = handler()->Compute(idle_time_ms, heap_state);
@@ -698,5 +698,21 @@ TEST_F(GCIdleTimeHandlerTest, BackgroundReduceLatencyToReduceMemory) {
   EXPECT_EQ(GCIdleTimeHandler::kReduceMemory, handler()->mode());
 }
 
+
+TEST_F(GCIdleTimeHandlerTest, SkipUselessGCs) {
+  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  heap_state.incremental_marking_stopped = false;
+  heap_state.can_start_incremental_marking = true;
+  TransitionToReduceMemoryMode(heap_state);
+  EXPECT_EQ(GCIdleTimeHandler::kReduceMemory, handler()->mode());
+  double idle_time_ms = GCIdleTimeHandler::kMinLongIdleTime;
+  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+  handler()->NotifyMarkCompact(false);
+  handler()->NotifyIdleMarkCompact();
+  action = handler()->Compute(idle_time_ms, heap_state);
+  EXPECT_EQ(DONE, action.type);
+}
+
 }  // namespace internal
 }  // namespace v8