[heap] New heuristics for starting of incremental marking.

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/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/context-slot-cache.h"
 #include "src/base/bits.h"
@@ skipping 249 matching lines @@
     isolate_->counters()->gc_compactor_caused_by_request()->Increment();
     *reason = "GC in old space requested";
     return MARK_COMPACTOR;
   }
 
   if (FLAG_gc_global || (FLAG_stress_compaction && (gc_count_ & 1) != 0)) {
     *reason = "GC in old space forced by flags";
     return MARK_COMPACTOR;
   }
 
-  // Is enough data promoted to justify a global GC?
-  if (OldGenerationAllocationLimitReached()) {
-    isolate_->counters()->gc_compactor_caused_by_promoted_data()->Increment();
-    *reason = "promotion limit reached";
-    return MARK_COMPACTOR;
-  }
-
   // Is there enough space left in OLD to guarantee that a scavenge can
   // succeed?
   //
   // Note that MemoryAllocator->MaxAvailable() undercounts the memory available
   // for object promotion. It counts only the bytes that the memory
   // allocator has not yet allocated from the OS and assigned to any space,
   // and does not count available bytes already in the old space or code
   // space.  Undercounting is safe---we may get an unrequested full GC when
   // a scavenge would have succeeded.
   if (memory_allocator()->MaxAvailable() <= new_space_->Size()) {
@@ skipping 770 matching lines @@
                                    GarbageCollectionReason gc_reason,
                                    GCCallbackFlags gc_callback_flags) {
   DCHECK(incremental_marking()->IsStopped());
   set_current_gc_flags(gc_flags);
   current_gc_callback_flags_ = gc_callback_flags;
   incremental_marking()->Start(gc_reason);
 }
 
 void Heap::StartIncrementalMarkingIfAllocationLimitIsReached(
     int gc_flags, const GCCallbackFlags gc_callback_flags) {
-  if (incremental_marking()->IsStopped() &&
-      incremental_marking()->ShouldActivateEvenWithoutIdleNotification()) {
-    StartIncrementalMarking(gc_flags, GarbageCollectionReason::kAllocationLimit,
-                            gc_callback_flags);
+  if (incremental_marking()->IsStopped()) {
+    IncrementalMarkingLimit reached_limit = ReachedIncrementalMarkingLimit();
+    if (reached_limit == IncrementalMarkingLimit::kSoftLimit) {
+      incremental_marking()->incremental_marking_job()->ScheduleTask(this);
+    } else if (reached_limit == IncrementalMarkingLimit::kHardLimit) {
+      StartIncrementalMarking(gc_flags,
+                              GarbageCollectionReason::kAllocationLimit,
+                              gc_callback_flags);
+    }
   }
 }
 
 void Heap::StartIdleIncrementalMarking(GarbageCollectionReason gc_reason) {
   gc_idle_time_handler_->ResetNoProgressCounter();
   StartIncrementalMarking(kReduceMemoryFootprintMask, gc_reason,
                           kNoGCCallbackFlags);
 }
 
 
@@ skipping 4230 matching lines @@
       CalculateOldGenerationAllocationLimit(factor, old_gen_size);
 
   if (FLAG_trace_gc_verbose) {
     isolate_->PrintWithTimestamp("Grow: old size: %" V8PRIdPTR
                                  " KB, new limit: %" V8PRIdPTR " KB (%.1f)\n",
                                  old_gen_size / KB,
                                  old_generation_allocation_limit_ / KB, factor);
   }
 }
 
-
 void Heap::DampenOldGenerationAllocationLimit(intptr_t old_gen_size,
                                               double gc_speed,
                                               double mutator_speed) {
   double factor = HeapGrowingFactor(gc_speed, mutator_speed);
   intptr_t limit = CalculateOldGenerationAllocationLimit(factor, old_gen_size);
   if (limit < old_generation_allocation_limit_) {
     if (FLAG_trace_gc_verbose) {
       isolate_->PrintWithTimestamp(
           "Dampen: old size: %" V8PRIdPTR " KB, old limit: %" V8PRIdPTR
           " KB, "
           "new limit: %" V8PRIdPTR " KB (%.1f)\n",
           old_gen_size / KB, old_generation_allocation_limit_ / KB, limit / KB,
           factor);
     }
     old_generation_allocation_limit_ = limit;
   }
 }
 
+// This predicate is called when an old generation space cannot allocated from
+// the free list and is about to add a new page. Returning false will cause a
+// major GC. It happens when the old generation allocation limit is reached and
+// - either we need to optimize for memory usage,
+// - or the incremental marking is not in progress and we cannot start it.
+bool Heap::ShouldExpandOldGenerationOnAllocationFailure() {
+  if (always_allocate() || OldGenerationSpaceAvailable() > 0) return true;
+  // We reached the old generation allocation limit.
+
+  if (ShouldOptimizeForMemoryUsage()) return false;
+
+  if (incremental_marking()->IsStopped() &&
+      ReachedIncrementalMarkingLimit() == IncrementalMarkingLimit::kNoLimit) {
+    // We cannot start incremental marking.
+    return false;
+  }
+  return true;
+}
+
+// This function returns either kNoLimit, kSoftLimit, or kHardLimit.
+// The kNoLimit means that either incremental marking is disabled or it is too
+// early to start incremental marking.
+// The kSoftLimit means that incremental marking should be started soon.
+// The kHardLimit means that incremental marking should be started immediately.
+Heap::IncrementalMarkingLimit Heap::ReachedIncrementalMarkingLimit() {

[Hannes Payer (out of office), 2016/09/27 09:16:53]

nit: maybe rename to IncrementalMarkingLimitReached

and rename the enum items to k*Reached

[ulan, 2016/09/27 17:06:41]

Renamed the function.

+  if (!incremental_marking()->CanBeActivated() ||
+      PromotedSpaceSizeOfObjects() < IncrementalMarking::kActivationThreshold) {
+    // Incremental marking is disabled or it is too early to start.
+    return IncrementalMarkingLimit::kNoLimit;
+  }
+  if ((FLAG_stress_compaction && (gc_count_ & 1) != 0) ||
+      HighMemoryPressure()) {
+    // If there is high memory pressure or stress testing is enabled, then
+    // start marking immediately.
+    return IncrementalMarkingLimit::kHardLimit;
+  }
+  intptr_t old_generation_space_available = OldGenerationSpaceAvailable();
+  if (old_generation_space_available > new_space_->Capacity()) {
+    return IncrementalMarkingLimit::kNoLimit;
+  }
+  // We are close to the allocation limit.
+  // Choose between the hard and the soft limits.
+  if (old_generation_space_available <= 0 || ShouldOptimizeForMemoryUsage()) {
+    return IncrementalMarkingLimit::kHardLimit;
+  }
+  return IncrementalMarkingLimit::kSoftLimit;
+}
 
 void Heap::EnableInlineAllocation() {
   if (!inline_allocation_disabled_) return;
   inline_allocation_disabled_ = false;
 
   // Update inline allocation limit for new space.
   new_space()->UpdateInlineAllocationLimit(0);
 }
 
 
@@ skipping 1147 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8