Add mode to reduce memory usage in idle notification.

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

 // Copyright 2014 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 <limits>
 
 #include "src/heap/gc-idle-time-handler.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace v8 {
@@ skipping 20 matching lines @@
     result.mark_compact_speed_in_bytes_per_ms = kMarkCompactSpeed;
     result.incremental_marking_speed_in_bytes_per_ms = kMarkingSpeed;
     result.scavenge_speed_in_bytes_per_ms = kScavengeSpeed;
     result.used_new_space_size = 0;
     result.new_space_capacity = kNewSpaceCapacity;
     result.new_space_allocation_throughput_in_bytes_per_ms =
         kNewSpaceAllocationThroughput;
     return result;
   }
 
+  void TransitionToReduceMemoryMode(
+      const GCIdleTimeHandler::HeapState& heap_state) {
+    handler()->NotifyScavenge();
+    double idle_time_ms = GCIdleTimeHandler::kMinLongIdleTime;
+    int limit = GCIdleTimeHandler::kLongIdleNotificationsBeforeMutatorIsIdle;
+    bool incremental = !heap_state.incremental_marking_stopped ||
+                       heap_state.can_start_incremental_marking;
+    for (int i = 0; i < limit; i++) {
+      GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+      EXPECT_EQ(incremental ? DO_INCREMENTAL_MARKING : DO_NOTHING, action.type);
+    }
+  }
+
+  void TransitionToDoneMode(const GCIdleTimeHandler::HeapState& heap_state,
+                            double idle_time_ms,
+                            GCIdleTimeActionType expected) {
+    int limit = GCIdleTimeHandler::kMaxIdleMarkCompacts;
+    for (int i = 0; i < limit; i++) {
+      GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+      EXPECT_EQ(expected, action.type);
+      EXPECT_EQ(true, action.reduce_memory);

[Erik Corry, 2015/05/05 21:38:52]

EXPECT_TRUE(action.reduce_memory)

[ulan, 2015/05/06 09:47:19]

Done.

+      handler()->NotifyMarkCompact();
+      handler()->NotifyIdleMarkCompact();
+    }
+  }
+
+  void TransitionToReduceLatencyMode() {
+    int limit = GCIdleTimeHandler::kGCsBeforeMutatorIsActive;
+    for (int i = 0; i < limit; i++) {
+      if (i % 2 == 0) {
+        handler()->NotifyScavenge();

[Erik Corry, 2015/05/05 21:38:52]

In this test there are 7 GCs in a row without any idle notification, but I don't
think that's realistic or what we want to test.

[ulan, 2015/05/06 09:47:19]

Added call to Compute.

+      } else {
+        handler()->NotifyMarkCompact();
+      }
+    }
+  }
+
   static const size_t kSizeOfObjects = 100 * MB;
   static const size_t kMarkCompactSpeed = 200 * KB;
   static const size_t kMarkingSpeed = 200 * KB;
   static const size_t kScavengeSpeed = 100 * KB;
   static const size_t kNewSpaceCapacity = 1 * MB;
   static const size_t kNewSpaceAllocationThroughput = 10 * KB;
+  static const int kMaxNotifications = 100;
 
  private:
   GCIdleTimeHandler handler_;
 };
 
 }  // namespace
 
 
 TEST(GCIdleTimeHandler, EstimateMarkingStepSizeInitial) {
   size_t step_size = GCIdleTimeHandler::EstimateMarkingStepSize(1, 0);
@@ skipping 49 matching lines @@
 TEST(GCIdleTimeHandler, EstimateMarkCompactTimeMax) {
   size_t size = std::numeric_limits<size_t>::max();
   size_t speed = 1;
   size_t time = GCIdleTimeHandler::EstimateMarkCompactTime(size, speed);
   EXPECT_EQ(GCIdleTimeHandler::kMaxMarkCompactTimeInMs, time);
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, DoScavengeEmptyNewSpace) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-  int idle_time_in_ms = 16;
+  int idle_time_ms = 16;
   EXPECT_FALSE(GCIdleTimeHandler::ShouldDoScavenge(
-      idle_time_in_ms, heap_state.new_space_capacity,
+      idle_time_ms, heap_state.new_space_capacity,
       heap_state.used_new_space_size, heap_state.scavenge_speed_in_bytes_per_ms,
       heap_state.new_space_allocation_throughput_in_bytes_per_ms));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, DoScavengeFullNewSpace) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.used_new_space_size = kNewSpaceCapacity;
-  int idle_time_in_ms = 16;
+  int idle_time_ms = 16;
   EXPECT_TRUE(GCIdleTimeHandler::ShouldDoScavenge(
-      idle_time_in_ms, heap_state.new_space_capacity,
+      idle_time_ms, heap_state.new_space_capacity,
       heap_state.used_new_space_size, heap_state.scavenge_speed_in_bytes_per_ms,
       heap_state.new_space_allocation_throughput_in_bytes_per_ms));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, DoScavengeUnknownScavengeSpeed) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.used_new_space_size = kNewSpaceCapacity;
   heap_state.scavenge_speed_in_bytes_per_ms = 0;
-  int idle_time_in_ms = 8;
+  int idle_time_ms = 8;
   EXPECT_FALSE(GCIdleTimeHandler::ShouldDoScavenge(
-      idle_time_in_ms, heap_state.new_space_capacity,
+      idle_time_ms, heap_state.new_space_capacity,
       heap_state.used_new_space_size, heap_state.scavenge_speed_in_bytes_per_ms,
       heap_state.new_space_allocation_throughput_in_bytes_per_ms));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, DoScavengeLowScavengeSpeed) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.used_new_space_size = kNewSpaceCapacity;
   heap_state.scavenge_speed_in_bytes_per_ms = 1 * KB;
-  int idle_time_in_ms = 16;
+  int idle_time_ms = 16;
   EXPECT_FALSE(GCIdleTimeHandler::ShouldDoScavenge(
-      idle_time_in_ms, heap_state.new_space_capacity,
+      idle_time_ms, heap_state.new_space_capacity,
       heap_state.used_new_space_size, heap_state.scavenge_speed_in_bytes_per_ms,
       heap_state.new_space_allocation_throughput_in_bytes_per_ms));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, DoScavengeHighScavengeSpeed) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.used_new_space_size = kNewSpaceCapacity;
   heap_state.scavenge_speed_in_bytes_per_ms = kNewSpaceCapacity;
-  int idle_time_in_ms = 16;
+  int idle_time_ms = 16;
   EXPECT_TRUE(GCIdleTimeHandler::ShouldDoScavenge(
-      idle_time_in_ms, heap_state.new_space_capacity,
+      idle_time_ms, heap_state.new_space_capacity,
       heap_state.used_new_space_size, heap_state.scavenge_speed_in_bytes_per_ms,
       heap_state.new_space_allocation_throughput_in_bytes_per_ms));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, ShouldDoMarkCompact) {
-  size_t idle_time_in_ms = GCIdleTimeHandler::kMaxScheduledIdleTime;
-  EXPECT_TRUE(GCIdleTimeHandler::ShouldDoMarkCompact(idle_time_in_ms, 0, 0));
+  size_t idle_time_ms = GCIdleTimeHandler::kMaxScheduledIdleTime;
+  EXPECT_TRUE(GCIdleTimeHandler::ShouldDoMarkCompact(idle_time_ms, 0, 0));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, DontDoMarkCompact) {
-  size_t idle_time_in_ms = 1;
+  size_t idle_time_ms = 1;
   EXPECT_FALSE(GCIdleTimeHandler::ShouldDoMarkCompact(
-      idle_time_in_ms, kSizeOfObjects, kMarkingSpeed));
+      idle_time_ms, kSizeOfObjects, kMarkingSpeed));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, ShouldDoFinalIncrementalMarkCompact) {
-  size_t idle_time_in_ms = 16;
+  size_t idle_time_ms = 16;
   EXPECT_TRUE(GCIdleTimeHandler::ShouldDoFinalIncrementalMarkCompact(
-      idle_time_in_ms, 0, 0));
+      idle_time_ms, 0, 0));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, DontDoFinalIncrementalMarkCompact) {
-  size_t idle_time_in_ms = 1;
+  size_t idle_time_ms = 1;
   EXPECT_FALSE(GCIdleTimeHandler::ShouldDoFinalIncrementalMarkCompact(
-      idle_time_in_ms, kSizeOfObjects, kMarkingSpeed));
+      idle_time_ms, kSizeOfObjects, kMarkingSpeed));
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, ContextDisposeLowRate) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.contexts_disposed = 1;
   heap_state.incremental_marking_stopped = true;
   double idle_time_ms = 0;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_NOTHING, action.type);
+  for (int mode = 0; mode < 1; mode++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_NOTHING, action.type);
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, ContextDisposeHighRate) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.contexts_disposed = 1;
   heap_state.contexts_disposal_rate =
       GCIdleTimeHandler::kHighContextDisposalRate - 1;
   heap_state.incremental_marking_stopped = true;
   double idle_time_ms = 0;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_FULL_GC, action.type);
+  for (int mode = 0; mode < 1; mode++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_FULL_GC, action.type);
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
-TEST_F(GCIdleTimeHandlerTest, AfterContextDisposeLargeIdleTime) {
-  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-  heap_state.contexts_disposed = 1;
-  heap_state.contexts_disposal_rate = 1.0;
-  heap_state.incremental_marking_stopped = true;
-  heap_state.can_start_incremental_marking = false;
-  size_t speed = heap_state.mark_compact_speed_in_bytes_per_ms;
-  double idle_time_ms =
-      static_cast<double>((heap_state.size_of_objects + speed - 1) / speed);
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_FULL_GC, action.type);
-}
-
-
 TEST_F(GCIdleTimeHandlerTest, AfterContextDisposeZeroIdleTime) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.contexts_disposed = 1;
   heap_state.contexts_disposal_rate = 1.0;
   heap_state.incremental_marking_stopped = true;
   double idle_time_ms = 0;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_FULL_GC, action.type);
+  for (int mode = 0; mode < 1; mode++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_FULL_GC, action.type);
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, AfterContextDisposeSmallIdleTime1) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.contexts_disposed = 1;
   heap_state.contexts_disposal_rate = 1.0;
   heap_state.incremental_marking_stopped = true;
   size_t speed = heap_state.mark_compact_speed_in_bytes_per_ms;
   double idle_time_ms =
       static_cast<double>(heap_state.size_of_objects / speed - 1);
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+  for (int mode = 0; mode < 1; mode++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, AfterContextDisposeSmallIdleTime2) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.contexts_disposed = 1;
   heap_state.contexts_disposal_rate = 1.0;
   size_t speed = heap_state.mark_compact_speed_in_bytes_per_ms;
   double idle_time_ms =
       static_cast<double>(heap_state.size_of_objects / speed - 1);
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+  for (int mode = 0; mode < 1; mode++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, IncrementalMarking1) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   size_t speed = heap_state.incremental_marking_speed_in_bytes_per_ms;
   double idle_time_ms = 10;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
-  EXPECT_GT(speed * static_cast<size_t>(idle_time_ms),
-            static_cast<size_t>(action.parameter));
-  EXPECT_LT(0, action.parameter);
+  for (int mode = 0; mode < 1; mode++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+    EXPECT_GT(speed * static_cast<size_t>(idle_time_ms),
+              static_cast<size_t>(action.parameter));
+    EXPECT_LT(0, action.parameter);
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, IncrementalMarking2) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.incremental_marking_stopped = true;
   size_t speed = heap_state.incremental_marking_speed_in_bytes_per_ms;
   double idle_time_ms = 10;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
-  EXPECT_GT(speed * static_cast<size_t>(idle_time_ms),
-            static_cast<size_t>(action.parameter));
-  EXPECT_LT(0, action.parameter);
+  for (int mode = 0; mode < 1; mode++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+    EXPECT_GT(speed * static_cast<size_t>(idle_time_ms),
+              static_cast<size_t>(action.parameter));
+    EXPECT_LT(0, action.parameter);
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, NotEnoughTime) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.incremental_marking_stopped = true;
   heap_state.can_start_incremental_marking = false;
   size_t speed = heap_state.mark_compact_speed_in_bytes_per_ms;
   double idle_time_ms =
       static_cast<double>(heap_state.size_of_objects / speed - 1);
   GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
   EXPECT_EQ(DO_NOTHING, action.type);
+  TransitionToReduceMemoryMode(heap_state);
+  action = handler()->Compute(idle_time_ms, heap_state);
+  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, FinalizeSweeping) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.incremental_marking_stopped = true;
   heap_state.can_start_incremental_marking = false;
-  heap_state.sweeping_in_progress = true;
-  heap_state.sweeping_completed = true;
-  double idle_time_ms = 10.0;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_FINALIZE_SWEEPING, action.type);
+  for (int mode = 0; mode < 1; mode++) {
+    heap_state.sweeping_in_progress = true;
+    heap_state.sweeping_completed = true;
+    double idle_time_ms = 10.0;
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_FINALIZE_SWEEPING, action.type);
+    heap_state.sweeping_in_progress = false;
+    heap_state.sweeping_completed = false;
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, CannotFinalizeSweeping) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.incremental_marking_stopped = true;
   heap_state.can_start_incremental_marking = false;
-  heap_state.sweeping_in_progress = true;
-  heap_state.sweeping_completed = false;
-  double idle_time_ms = 10.0;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_NOTHING, action.type);
+  for (int mode = 0; mode < 1; mode++) {
+    heap_state.sweeping_in_progress = true;
+    heap_state.sweeping_completed = false;
+    double idle_time_ms = 10.0;
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_NOTHING, action.type);
+    heap_state.sweeping_in_progress = false;
+    heap_state.sweeping_completed = false;
+    TransitionToReduceMemoryMode(heap_state);
+  }
 }
 
 
+TEST_F(GCIdleTimeHandlerTest, Scavenge) {
+  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  int idle_time_ms = 10;
+  for (int mode = 0; mode < 1; mode++) {
+    heap_state.used_new_space_size =
+        heap_state.new_space_capacity -
+        (kNewSpaceAllocationThroughput * idle_time_ms);
+    GCIdleTimeAction action =
+        handler()->Compute(static_cast<double>(idle_time_ms), heap_state);
+    EXPECT_EQ(DO_SCAVENGE, action.type);
+    heap_state.used_new_space_size = 0;
+    TransitionToReduceMemoryMode(heap_state);
+  }
+}
+
+
+TEST_F(GCIdleTimeHandlerTest, ScavengeAndDone) {
+  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  int idle_time_ms = 10;
+  heap_state.can_start_incremental_marking = false;
+  heap_state.incremental_marking_stopped = true;
+  for (int mode = 0; mode < 1; mode++) {
+    heap_state.used_new_space_size =
+        heap_state.new_space_capacity -
+        (kNewSpaceAllocationThroughput * idle_time_ms);
+    GCIdleTimeAction action =
+        handler()->Compute(static_cast<double>(idle_time_ms), heap_state);
+    EXPECT_EQ(DO_SCAVENGE, action.type);
+    heap_state.used_new_space_size = 0;
+    action = handler()->Compute(static_cast<double>(idle_time_ms), heap_state);
+    EXPECT_EQ(DO_NOTHING, action.type);
+    TransitionToReduceMemoryMode(heap_state);
+  }
+}
+
+
 TEST_F(GCIdleTimeHandlerTest, StopEventually1) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.incremental_marking_stopped = true;
   heap_state.can_start_incremental_marking = false;
+  double idle_time_ms = GCIdleTimeHandler::kMinLongIdleTime;
+  bool stopped = false;
+  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()->NotifyIdleMarkCompact();
+    }
+    if (action.type == DONE) stopped = true;
+  }
+  EXPECT_TRUE(stopped);
+}
+
+
+TEST_F(GCIdleTimeHandlerTest, StopEventually2) {
+  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  heap_state.incremental_marking_stopped = true;
+  heap_state.can_start_incremental_marking = false;
   size_t speed = heap_state.mark_compact_speed_in_bytes_per_ms;
   double idle_time_ms =
       static_cast<double>(heap_state.size_of_objects / speed + 1);
-  for (int i = 0; i < GCIdleTimeHandler::kMaxMarkCompactsInIdleRound; i++) {
-    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-    EXPECT_EQ(DO_FULL_GC, action.type);
-    handler()->NotifyIdleMarkCompact();
-  }
+  TransitionToReduceMemoryMode(heap_state);
+  TransitionToDoneMode(heap_state, idle_time_ms, DO_FULL_GC);
   GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
   EXPECT_EQ(DONE, action.type);
 }
 
 
-TEST_F(GCIdleTimeHandlerTest, StopEventually2) {
+TEST_F(GCIdleTimeHandlerTest, StopEventually3) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  heap_state.incremental_marking_stopped = true;
+  heap_state.can_start_incremental_marking = false;
   double idle_time_ms = 10;
-  for (int i = 0; i < GCIdleTimeHandler::kMaxMarkCompactsInIdleRound; i++) {
-    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
-    // In this case we emulate incremental marking steps that finish with a
-    // full gc.
-    handler()->NotifyIdleMarkCompact();
-  }
-  heap_state.can_start_incremental_marking = false;
+  TransitionToReduceMemoryMode(heap_state);
+  TransitionToDoneMode(heap_state, idle_time_ms, DO_INCREMENTAL_MARKING);
   GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
   EXPECT_EQ(DONE, action.type);
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, ContinueAfterStop1) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.incremental_marking_stopped = true;
   heap_state.can_start_incremental_marking = false;
   size_t speed = heap_state.mark_compact_speed_in_bytes_per_ms;
   double idle_time_ms =
       static_cast<double>(heap_state.size_of_objects / speed + 1);
-  for (int i = 0; i < GCIdleTimeHandler::kMaxMarkCompactsInIdleRound; i++) {
-    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-    EXPECT_EQ(DO_FULL_GC, action.type);
-    handler()->NotifyIdleMarkCompact();
-  }
+  TransitionToReduceMemoryMode(heap_state);
+  TransitionToDoneMode(heap_state, idle_time_ms, DO_FULL_GC);
   GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
   EXPECT_EQ(DONE, action.type);
-  // Emulate mutator work.
-  for (int i = 0; i < GCIdleTimeHandler::kIdleScavengeThreshold; i++) {
-    handler()->NotifyScavenge();
-  }
+  TransitionToReduceLatencyMode();
+  heap_state.can_start_incremental_marking = true;
   action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_FULL_GC, action.type);
+  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+  EXPECT_FALSE(action.reduce_memory);
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, ContinueAfterStop2) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  heap_state.incremental_marking_stopped = true;
+  heap_state.can_start_incremental_marking = false;
   double idle_time_ms = 10;
-  for (int i = 0; i < GCIdleTimeHandler::kMaxMarkCompactsInIdleRound; i++) {
-    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-    if (action.type == DONE) break;
-    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
-    // In this case we try to emulate incremental marking steps the finish with
-    // a full gc.
-    handler()->NotifyIdleMarkCompact();
-  }
-  heap_state.can_start_incremental_marking = false;
+  TransitionToReduceMemoryMode(heap_state);
+  TransitionToDoneMode(heap_state, idle_time_ms, DO_INCREMENTAL_MARKING);
   GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
   EXPECT_EQ(DONE, action.type);
-  // Emulate mutator work.
-  for (int i = 0; i < GCIdleTimeHandler::kIdleScavengeThreshold; i++) {
-    handler()->NotifyScavenge();
-  }
+  TransitionToReduceLatencyMode();
   heap_state.can_start_incremental_marking = true;
   action = handler()->Compute(idle_time_ms, heap_state);
   EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
-}
-
-
-TEST_F(GCIdleTimeHandlerTest, Scavenge) {
-  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-  int idle_time_ms = 10;
-  heap_state.used_new_space_size =
-      heap_state.new_space_capacity -
-      (kNewSpaceAllocationThroughput * idle_time_ms);
-  GCIdleTimeAction action =
-      handler()->Compute(static_cast<double>(idle_time_ms), heap_state);
-  EXPECT_EQ(DO_SCAVENGE, action.type);
-}
-
-
-TEST_F(GCIdleTimeHandlerTest, ScavengeAndDone) {
-  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-  int idle_time_ms = 10;
-  heap_state.can_start_incremental_marking = false;
-  heap_state.incremental_marking_stopped = true;
-  heap_state.used_new_space_size =
-      heap_state.new_space_capacity -
-      (kNewSpaceAllocationThroughput * idle_time_ms);
-  GCIdleTimeAction action =
-      handler()->Compute(static_cast<double>(idle_time_ms), heap_state);
-  EXPECT_EQ(DO_SCAVENGE, action.type);
-  heap_state.used_new_space_size = 0;
-  action = handler()->Compute(static_cast<double>(idle_time_ms), heap_state);
-  EXPECT_EQ(DO_NOTHING, action.type);
+  EXPECT_FALSE(action.reduce_memory);
 }
 
 
 TEST_F(GCIdleTimeHandlerTest, ZeroIdleTimeNothingToDo) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-  double idle_time_ms = 0;
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DO_NOTHING, action.type);
+  for (int i = 0; i < kMaxNotifications; i++) {
+    GCIdleTimeAction action = handler()->Compute(0, heap_state);
+    EXPECT_EQ(DO_NOTHING, action.type);
+  }
 }
 
 
-TEST_F(GCIdleTimeHandlerTest, ZeroIdleTimeDoNothingButStartIdleRound) {
+TEST_F(GCIdleTimeHandlerTest, SmallIdleTimeNothingToDo) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-  double idle_time_ms = 10;
-  for (int i = 0; i < GCIdleTimeHandler::kMaxMarkCompactsInIdleRound; i++) {
-    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-    if (action.type == DONE) break;
-    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
-    // In this case we try to emulate incremental marking steps the finish with
-    // a full gc.
-    handler()->NotifyIdleMarkCompact();
+  heap_state.incremental_marking_stopped = true;
+  heap_state.can_start_incremental_marking = false;
+  for (int i = 0; i < kMaxNotifications; i++) {
+    GCIdleTimeAction action = handler()->Compute(10, heap_state);
+    EXPECT_EQ(DO_NOTHING, action.type);
   }
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  // Emulate mutator work.
-  for (int i = 0; i < GCIdleTimeHandler::kIdleScavengeThreshold; i++) {
-    handler()->NotifyScavenge();
-  }
-  action = handler()->Compute(0, heap_state);
-  EXPECT_EQ(DO_NOTHING, action.type);
 }
 
 
-TEST_F(GCIdleTimeHandlerTest, KeepDoingDoNothingWithZeroIdleTime) {
+TEST_F(GCIdleTimeHandlerTest, StayInReduceLatencyModeBecauseOfScavenges) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-  for (int i = 0; i < GCIdleTimeHandler::kMaxNoProgressIdleTimesPerIdleRound;
-       i++) {
-    GCIdleTimeAction action = handler()->Compute(0, heap_state);
+  heap_state.incremental_marking_stopped = true;
+  heap_state.can_start_incremental_marking = false;
+  double idle_time_ms = GCIdleTimeHandler::kMinLongIdleTime;
+  int limit = GCIdleTimeHandler::kLongIdleNotificationsBeforeMutatorIsIdle;
+  for (int i = 0; i < kMaxNotifications; i++) {
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
     EXPECT_EQ(DO_NOTHING, action.type);
+    if ((i + 1) % limit == 0) handler()->NotifyScavenge();
   }
-  // Should still return DO_NOTHING if we have been given 0 deadline yet.
-  GCIdleTimeAction action = handler()->Compute(0, heap_state);
-  EXPECT_EQ(DO_NOTHING, action.type);
 }
 
 
-TEST_F(GCIdleTimeHandlerTest, DoneIfNotMakingProgressOnSweeping) {
+TEST_F(GCIdleTimeHandlerTest, StayInReduceLatencyModeBecauseOfMarkCompacts) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-
-  // Simulate sweeping being in-progress but not complete.
   heap_state.incremental_marking_stopped = true;
   heap_state.can_start_incremental_marking = false;
-  heap_state.sweeping_in_progress = true;
-  heap_state.sweeping_completed = false;
-  double idle_time_ms = 10.0;
-  for (int i = 0; i < GCIdleTimeHandler::kMaxNoProgressIdleTimesPerIdleRound;
-       i++) {
+  double idle_time_ms = GCIdleTimeHandler::kMinLongIdleTime;
+  int limit = GCIdleTimeHandler::kLongIdleNotificationsBeforeMutatorIsIdle;
+  for (int i = 0; i < kMaxNotifications; i++) {
     GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
     EXPECT_EQ(DO_NOTHING, action.type);
+    if ((i + 1) % limit == 0) handler()->NotifyMarkCompact();
   }
-  // We should return DONE after not making progress for some time.
+}
+
+
+TEST_F(GCIdleTimeHandlerTest, ReduceMemoryToReduceLatency) {
+  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  heap_state.incremental_marking_stopped = true;
+  heap_state.can_start_incremental_marking = false;
+  double idle_time_ms = GCIdleTimeHandler::kMinLongIdleTime;
+  int limit = GCIdleTimeHandler::kMaxIdleMarkCompacts;
+  for (int idle_gc = 0; idle_gc < limit; idle_gc++) {
+    TransitionToReduceMemoryMode(heap_state);
+    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+    EXPECT_TRUE(action.reduce_memory);
+    for (int i = 0; i < idle_gc; i++) {
+      action = handler()->Compute(idle_time_ms, heap_state);
+      EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+      EXPECT_TRUE(action.reduce_memory);
+      // ReduceMemory mode should tolerate one mutator GC per idle GC.
+      handler()->NotifyScavenge();
+      // Notify idle GC.
+      handler()->NotifyMarkCompact();
+      handler()->NotifyIdleMarkCompact();
+    }
+    // Transition to ReduceLatency mode after doing |idle_gc| idle GCs.
+    handler()->NotifyScavenge();
+    action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_NOTHING, action.type);
+    EXPECT_FALSE(action.reduce_memory);
+  }
+}
+
+
+TEST_F(GCIdleTimeHandlerTest, ReduceMemoryToDone) {
+  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  heap_state.incremental_marking_stopped = true;
+  heap_state.can_start_incremental_marking = false;
+  double idle_time_ms = GCIdleTimeHandler::kMinLongIdleTime;
+  int limit = GCIdleTimeHandler::kMaxIdleMarkCompacts;
+  TransitionToReduceMemoryMode(heap_state);
   GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+  EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+  EXPECT_TRUE(action.reduce_memory);
+  for (int i = 0; i < limit; i++) {
+    action = handler()->Compute(idle_time_ms, heap_state);
+    EXPECT_EQ(DO_INCREMENTAL_MARKING, action.type);
+    EXPECT_TRUE(action.reduce_memory);
+    // ReduceMemory mode should tolerate one mutator GC per idle GC.
+    handler()->NotifyScavenge();
+    // Notify idle GC.
+    handler()->NotifyMarkCompact();
+    handler()->NotifyIdleMarkCompact();
+  }
+  action = handler()->Compute(idle_time_ms, heap_state);
   EXPECT_EQ(DONE, action.type);
 }
 
 
-TEST_F(GCIdleTimeHandlerTest, DoneIfNotMakingProgressOnIncrementalMarking) {
-  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
-
-  // Simulate incremental marking stopped and not eligible to start.
-  heap_state.incremental_marking_stopped = true;
-  heap_state.can_start_incremental_marking = false;
-  double idle_time_ms = 10.0;
-  for (int i = 0; i < GCIdleTimeHandler::kMaxNoProgressIdleTimesPerIdleRound;
-       i++) {
-    GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-    EXPECT_EQ(DO_NOTHING, action.type);
-  }
-  // We should return DONE after not making progress for some time.
-  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
-  EXPECT_EQ(DONE, action.type);
-}
-
 }  // namespace internal
 }  // namespace v8