Use actual incremental marking throughput in IdleNotification to estimate marking step size.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index fd08c8292f812c8c3084fb699eb9f65dcc98b4a7..40ff03f49c9b98c5ce61bc4fff8161ead6d09426 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -4259,7 +4259,26 @@ void Heap::MakeHeapIterable() {
 }
 
 
-void Heap::AdvanceIdleIncrementalMarking(intptr_t step_size) {
+intptr_t Heap::EstimateMarkingStepSize(int idle_time_in_ms) {
+  // We have to make sure that we finish the IdleNotification before
+  // idle_time_in_ms. Hence, we conservatively prune our workload estimate.
+  const double kConservativeTimeRatio = 0.9;
+  // If we haven't recorded any incremental marking events yet, we carefully
+  // mark with a conservative lower bound for the marking speed.
+  const intptr_t kMarkingSpeedInBytesLowerBound = 100 * KB;
+  intptr_t marking_speed_in_bytes_per_millisecond =
+      tracer_.IncrementalMarkingSpeedInBytesPerMillisecond();
+  if (marking_speed_in_bytes_per_millisecond == 0) {
+    marking_speed_in_bytes_per_millisecond = kMarkingSpeedInBytesLowerBound;
+  }
+  return static_cast<intptr_t>(marking_speed_in_bytes_per_millisecond *

[ulan, 2014/08/18 12:32:13]

Potential integer overflow here, maybe use marking_speed_in_kilobytes?

[Hannes Payer (out of office), 2014/08/19 15:24:04]

Good catch.

+                               kConservativeTimeRatio * idle_time_in_ms);
+}
+
+
+void Heap::AdvanceIdleIncrementalMarking(int idle_time_in_ms) {
+  intptr_t step_size = EstimateMarkingStepSize(idle_time_in_ms);
+
   incremental_marking()->Step(step_size,
                               IncrementalMarking::NO_GC_VIA_STACK_GUARD, true);
 
@@ -4282,36 +4301,27 @@ void Heap::AdvanceIdleIncrementalMarking(intptr_t step_size) {
 }
 
 
-bool Heap::IdleNotification(int hint) {
+bool Heap::IdleNotification(int idle_time_in_ms) {
   // If incremental marking is off, we do not perform idle notification.
   if (!FLAG_incremental_marking) return true;
 
-  // Hints greater than this value indicate that
-  // the embedder is requesting a lot of GC work.
-  const int kMaxHint = 1000;
-  const int kMinHintForIncrementalMarking = 10;
   // Minimal hint that allows to do full GC.
   const int kMinHintForFullGC = 100;
-  intptr_t size_factor = Min(Max(hint, 20), kMaxHint) / 4;
-  // The size factor is in range [5..250]. The numbers here are chosen from
-  // experiments. If you changes them, make sure to test with
-  // chrome/performance_ui_tests --gtest_filter="GeneralMixMemoryTest.*
-  intptr_t step_size = size_factor * IncrementalMarking::kAllocatedThreshold;
-
-  isolate()->counters()->gc_idle_time_allotted_in_ms()->AddSample(hint);
+  isolate()->counters()->gc_idle_time_allotted_in_ms()->AddSample(
+      idle_time_in_ms);
   HistogramTimerScope idle_notification_scope(
       isolate_->counters()->gc_idle_notification());
 
   if (contexts_disposed_ > 0) {
     contexts_disposed_ = 0;
     int mark_sweep_time = Min(TimeMarkSweepWouldTakeInMs(), 1000);
-    if (hint >= mark_sweep_time && !FLAG_expose_gc &&
+    if (idle_time_in_ms >= mark_sweep_time && !FLAG_expose_gc &&
         incremental_marking()->IsStopped()) {
       HistogramTimerScope scope(isolate_->counters()->gc_context());
       CollectAllGarbage(kReduceMemoryFootprintMask,
                         "idle notification: contexts disposed");
     } else {
-      AdvanceIdleIncrementalMarking(step_size);
+      AdvanceIdleIncrementalMarking(idle_time_in_ms);
     }
 
     // After context disposal there is likely a lot of garbage remaining, reset
@@ -4346,17 +4356,16 @@ bool Heap::IdleNotification(int hint) {
     // the code space.
     // TODO(ulan): Once we enable code compaction for incremental marking,
     // we can get rid of this special case and always start incremental marking.
-    if (remaining_mark_sweeps <= 2 && hint >= kMinHintForFullGC) {
+    if (remaining_mark_sweeps <= 2 && idle_time_in_ms >= kMinHintForFullGC) {
       CollectAllGarbage(kReduceMemoryFootprintMask,
                         "idle notification: finalize idle round");
       mark_sweeps_since_idle_round_started_++;
-    } else if (hint > kMinHintForIncrementalMarking) {
+    } else {
       incremental_marking()->Start();
     }
   }
-  if (!incremental_marking()->IsStopped() &&
-      hint > kMinHintForIncrementalMarking) {
-    AdvanceIdleIncrementalMarking(step_size);
+  if (!incremental_marking()->IsStopped()) {
+    AdvanceIdleIncrementalMarking(idle_time_in_ms);
   }
 
   if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
@@ -4366,7 +4375,7 @@ bool Heap::IdleNotification(int hint) {
 
   // If the IdleNotifcation is called with a large hint we will wait for
   // the sweepter threads here.
-  if (hint >= kMinHintForFullGC &&
+  if (idle_time_in_ms >= kMinHintForFullGC &&
       mark_compact_collector()->sweeping_in_progress()) {
     mark_compact_collector()->EnsureSweepingCompleted();
   }