Start incremental marking on idle notification.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 4da83e859e3ddff3f2988c00f066ab63ddf58c04..8d36b87307006ff496f2ee622cb6faf93dde1731 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -143,6 +143,11 @@ Heap::Heap()
       number_idle_notifications_(0),
       last_idle_notification_gc_count_(0),
       last_idle_notification_gc_count_init_(false),
+      idle_notification_will_schedule_next_gc_(false),
+      mark_sweeps_since_idle_round_started_(0),
+      ms_count_at_last_idle_notification_(0),
+      gc_count_at_last_idle_gc_(0),
+      scavenges_since_last_idle_round_(kIdleScavengeThreshold),

[ulan, 2011/11/23 16:18:06]

The initial value allows to start the idle round on the first idle notification.

       configured_(false),
       chunks_queued_for_free_(NULL) {
   // Allow build-time customization of the max semispace size. Building
@@ -1010,8 +1015,7 @@ void Heap::Scavenge() {
 
   incremental_marking()->PrepareForScavenge();
 
-  old_pointer_space()->AdvanceSweeper(new_space_.Size());
-  old_data_space()->AdvanceSweeper(new_space_.Size());
+  AdvanceSweepers(new_space_.Size());
 
   // Flip the semispaces.  After flipping, to space is empty, from space has
   // live objects.
@@ -1099,6 +1103,8 @@ void Heap::Scavenge() {
   LOG(isolate_, ResourceEvent("scavenge", "end"));
 
   gc_state_ = NOT_IN_GC;
+
+  scavenges_since_last_idle_round_++;
 }
 
 
@@ -4460,7 +4466,79 @@ void Heap::EnsureHeapIsIterable() {
 }
 
 
-bool Heap::IdleNotification() {
+bool Heap::IdleNotification(int hint) {
+  if (!FLAG_incremental_marking || FLAG_expose_gc) {
+    return hint < 1000 ? true : IdleGlobalGC();
+  }
+
+  // By doing small chunks of GC work in each IdleNotification,
+  // perform a round of incremental GCs and after that wait until
+  // the mutator creates enough garbage to justify a new round.
+  // An incremental GC progresses as follows:
+  // 1. many incremental marking steps,
+  // 2. one old space mark-sweep-compact,
+  // 3. many lazy sweep steps.
+  // Use mark-sweep-compact events to count incremental GCs in a round.
+
+  intptr_t size_factor = Min(Max(hint, 30), 1000) / 10;
+  // The size factor is in range [3..100].
+  intptr_t step_size = size_factor * IncrementalMarking::kAllocatedThreshold;
+
+  if (incremental_marking()->IsStopped()) {
+    if (!IsSweepingComplete() && !AdvanceSweepers(step_size)) {
+      return false;
+    }
+  }
+
+  if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
+    if (EnoughGarbageSinceLastIdleRound()) {
+      StartIdleRound();
+    } else {
+      return true;
+    }
+  }
+
+  int new_mark_sweeps = ms_count_ - ms_count_at_last_idle_notification_;
+  mark_sweeps_since_idle_round_started_ += new_mark_sweeps;
+  ms_count_at_last_idle_notification_ = ms_count_;
+
+  if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
+    FinishIdleRound();
+    return true;
+  }
+
+  if (incremental_marking()->IsStopped()) {
+    if (hint < 1000 && !WorthStartingGCWhenIdle()) {

[ulan, 2011/11/23 16:18:06]

If hint >= 1000 then the embedder is asking us to do a lot of GC work. This
helps to reduce the memory usage in Chrome memory tests.

+      FinishIdleRound();
+      return true;
+    }
+    incremental_marking()->Start();
+  }
+
+  // This flag prevents incremental marking from requesting GC via stack guard
+  idle_notification_will_schedule_next_gc_ = true;
+  incremental_marking()->Step(step_size);
+  idle_notification_will_schedule_next_gc_ = false;
+
+  if (incremental_marking()->IsComplete()) {
+    bool uncommit = false;
+    if (gc_count_at_last_idle_gc_ == gc_count_) {
+      // No GC since the last full GC, the mutator is probably not active.
+      isolate_->compilation_cache()->Clear();
+      uncommit = true;
+    }
+    CollectAllGarbage(kNoGCFlags);
+    gc_count_at_last_idle_gc_ = gc_count_;
+    if (uncommit) {
+      new_space_.Shrink();
+      UncommitFromSpace();
+    }
+  }
+  return false;
+}
+
+
+bool Heap::IdleGlobalGC() {
   static const int kIdlesBeforeScavenge = 4;
   static const int kIdlesBeforeMarkSweep = 7;
   static const int kIdlesBeforeMarkCompact = 8;