Uncommit and shrink semi-spaces only on low allocation rate.

src/heap/heap.cc

 // Copyright 2012 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/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 715 matching lines @@
 #undef UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE
 
 #ifdef DEBUG
   ReportStatisticsAfterGC();
 #endif  // DEBUG
 
   // Remember the last top pointer so that we can later find out
   // whether we allocated in new space since the last GC.
   new_space_top_after_last_gc_ = new_space()->top();
   last_gc_time_ = MonotonicallyIncreasingTimeInMs();
+
+  ReduceNewSpaceSize(
+      tracer()->CurrentNewSpaceAllocationThroughputInBytesPerMillisecond());
 }
 
 
 void Heap::PreprocessStackTraces() {
   if (!weak_stack_trace_list()->IsWeakFixedArray()) return;
   WeakFixedArray* array = WeakFixedArray::cast(weak_stack_trace_list());
   int length = array->Length();
   for (int i = 0; i < length; i++) {
     if (array->IsEmptySlot(i)) continue;
     FixedArray* elements = FixedArray::cast(array->Get(i));
@@ skipping 3816 matching lines @@
   if (!IsHeapIterable()) {
     CollectAllGarbage(kMakeHeapIterableMask, "Heap::MakeHeapIterable");
   }
   if (mark_compact_collector()->sweeping_in_progress()) {
     mark_compact_collector()->EnsureSweepingCompleted();
   }
   DCHECK(IsHeapIterable());
 }
 
 
-void Heap::ReduceNewSpaceSize(GCIdleTimeAction action) {
-  if (action.reduce_memory &&
-      (action.type == DO_SCAVENGE || action.type == DO_FULL_GC ||
-       (action.type == DO_INCREMENTAL_MARKING &&
-        incremental_marking()->IsStopped()))) {
+bool Heap::HasLowAllocationRate(size_t allocation_rate) {
+  static const size_t kLowAllocationRate = 1000;
+  if (allocation_rate == 0) return false;
+  return allocation_rate < kLowAllocationRate;
+}
+
+
+void Heap::ReduceNewSpaceSize(size_t allocation_rate) {
+  if (HasLowAllocationRate(allocation_rate)) {
     new_space_.Shrink();
     UncommitFromSpace();
   }
 }
 
 
 bool Heap::TryFinalizeIdleIncrementalMarking(
     double idle_time_in_ms, size_t size_of_objects,
     size_t final_incremental_mark_compact_speed_in_bytes_per_ms) {
   if (FLAG_overapproximate_weak_closure &&
@@ skipping 45 matching lines @@
       tracer()->IncrementalMarkingSpeedInBytesPerMillisecond());
   heap_state.final_incremental_mark_compact_speed_in_bytes_per_ms =
       static_cast<size_t>(
           tracer()->FinalIncrementalMarkCompactSpeedInBytesPerMillisecond());
   heap_state.scavenge_speed_in_bytes_per_ms =
       static_cast<size_t>(tracer()->ScavengeSpeedInBytesPerMillisecond());
   heap_state.used_new_space_size = new_space_.Size();
   heap_state.new_space_capacity = new_space_.Capacity();
   heap_state.new_space_allocation_throughput_in_bytes_per_ms =
       tracer()->NewSpaceAllocationThroughputInBytesPerMillisecond();
+  heap_state.current_new_space_allocation_throughput_in_bytes_per_ms =
+      tracer()->CurrentNewSpaceAllocationThroughputInBytesPerMillisecond();
   return heap_state;
 }
 
 
 bool Heap::PerformIdleTimeAction(GCIdleTimeAction action,
                                  GCIdleTimeHandler::HeapState heap_state,
                                  double deadline_in_ms,
                                  bool is_long_idle_notification) {
   bool result = false;
   switch (action.type) {
@@ skipping 42 matching lines @@
     case DO_SCAVENGE:
       CollectGarbage(NEW_SPACE, "idle notification: scavenge");
       break;
     case DO_FINALIZE_SWEEPING:
       mark_compact_collector()->EnsureSweepingCompleted();
       break;
     case DO_NOTHING:
       break;
   }
 
-  ReduceNewSpaceSize(action);
   return result;
 }
 
 
 void Heap::IdleNotificationEpilogue(GCIdleTimeAction action,
                                     GCIdleTimeHandler::HeapState heap_state,
                                     double start_ms, double deadline_in_ms,
                                     bool is_long_idle_notification) {
   double idle_time_in_ms = deadline_in_ms - start_ms;
   double current_time = MonotonicallyIncreasingTimeInMs();
@@ skipping 244 matching lines @@
 
   VerifyPointersVisitor no_dirty_regions_visitor;
   code_space_->Verify(&no_dirty_regions_visitor);
 
   lo_space_->Verify();
 }
 #endif
 
 
 void Heap::ZapFromSpace() {
+  if (!new_space_.IsFromSpaceCommitted()) return;
   NewSpacePageIterator it(new_space_.FromSpaceStart(),
                           new_space_.FromSpaceEnd());
   while (it.has_next()) {
     NewSpacePage* page = it.next();
     for (Address cursor = page->area_start(), limit = page->area_end();
          cursor < limit; cursor += kPointerSize) {
       Memory::Address_at(cursor) = kFromSpaceZapValue;
     }
   }
 }
@@ skipping 1612 matching lines @@
     *object_type = "CODE_TYPE";                                                \
     *object_sub_type = "CODE_AGE/" #name;                                      \
     return true;
     CODE_AGE_LIST_COMPLETE(COMPARE_AND_RETURN_NAME)
 #undef COMPARE_AND_RETURN_NAME
   }
   return false;
 }
 }
 }  // namespace v8::internal