Bring back high promotion mode to shrink young generation size when scavenging latency is high.

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 98 matching lines @@
       old_generation_allocation_limit_(initial_old_generation_size_),
       idle_old_generation_allocation_limit_(
           kMinimumOldGenerationAllocationLimit),
       old_gen_exhausted_(false),
       inline_allocation_disabled_(false),
       store_buffer_rebuilder_(store_buffer()),
       hidden_string_(NULL),
       gc_safe_size_of_old_object_(NULL),
       total_regexp_code_generated_(0),
       tracer_(this),
+      new_space_high_promotion_mode_active_(false),
       high_survival_rate_period_length_(0),
       promoted_objects_size_(0),
+      low_survival_rate_period_length_(0),
+      survival_rate_(0),
       promotion_ratio_(0),
       semi_space_copied_object_size_(0),
       previous_semi_space_copied_object_size_(0),
       semi_space_copied_rate_(0),
       nodes_died_in_new_space_(0),
       nodes_copied_in_new_space_(0),
       nodes_promoted_(0),
       maximum_size_scavenges_(0),
+      previous_survival_rate_trend_(Heap::STABLE),
+      survival_rate_trend_(Heap::STABLE),
       max_gc_pause_(0.0),
       total_gc_time_ms_(0.0),
       max_alive_after_gc_(0),
       min_in_mutator_(kMaxInt),
       marking_time_(0.0),
       sweeping_time_(0.0),
       last_idle_notification_time_(0.0),
       last_gc_time_(0.0),
       mark_compact_collector_(this),
       store_buffer_(this),
@@ skipping 1026 matching lines @@
       (static_cast<double>(semi_space_copied_object_size_) /
        static_cast<double>(start_new_space_size) * 100);
 
   double survival_rate = promotion_ratio_ + semi_space_copied_rate_;
   tracer()->AddSurvivalRatio(survival_rate);
   if (survival_rate > kYoungSurvivalRateHighThreshold) {
     high_survival_rate_period_length_++;
   } else {
     high_survival_rate_period_length_ = 0;
   }
+
+  if (survival_rate < kYoungSurvivalRateLowThreshold) {
+    low_survival_rate_period_length_++;
+  } else {
+    low_survival_rate_period_length_ = 0;
+  }
+
+  double survival_rate_diff = survival_rate_ - survival_rate;
+
+  if (survival_rate_diff > kYoungSurvivalRateAllowedDeviation) {
+    set_survival_rate_trend(DECREASING);
+  } else if (survival_rate_diff < -kYoungSurvivalRateAllowedDeviation) {
+    set_survival_rate_trend(INCREASING);
+  } else {
+    set_survival_rate_trend(STABLE);
+  }
+
+  survival_rate_ = survival_rate;
 }
 
 bool Heap::PerformGarbageCollection(
     GarbageCollector collector, const v8::GCCallbackFlags gc_callback_flags) {
   int freed_global_handles = 0;
 
   if (collector != SCAVENGER) {
     PROFILE(isolate_, CodeMovingGCEvent());
   }
 
@@ skipping 36 matching lines @@
     old_generation_size_configured_ = true;
   } else {
     Scavenge();
   }
 
   // This should be updated before PostGarbageCollectionProcessing, which can
   // cause another GC.
   old_generation_size_at_last_gc_ = PromotedSpaceSizeOfObjects();
 
   UpdateSurvivalStatistics(start_new_space_size);
+  ConfigureNewGenerationSize();
   ConfigureInitialOldGenerationSize();
 
   isolate_->counters()->objs_since_last_young()->Set(0);
 
   if (collector != SCAVENGER) {
     // Callbacks that fire after this point might trigger nested GCs and
     // restart incremental marking, the assertion can't be moved down.
     DCHECK(incremental_marking()->IsStopped());
 
     // We finished a marking cycle. We can uncommit the marking deque until
@@ skipping 197 matching lines @@
 void Heap::CheckNewSpaceExpansionCriteria() {
   if (FLAG_experimental_new_space_growth_heuristic) {
     if (new_space_.TotalCapacity() < new_space_.MaximumCapacity() &&
         survived_last_scavenge_ * 100 / new_space_.TotalCapacity() >= 10) {
       // Grow the size of new space if there is room to grow, and more than 10%
       // have survived the last scavenge.
       new_space_.Grow();
       survived_since_last_expansion_ = 0;
     }
   } else if (new_space_.TotalCapacity() < new_space_.MaximumCapacity() &&
-             survived_since_last_expansion_ > new_space_.TotalCapacity()) {
+             survived_since_last_expansion_ > new_space_.TotalCapacity() &&
+             !new_space_high_promotion_mode_active_) {
     // Grow the size of new space if there is room to grow, and enough data
     // has survived scavenge since the last expansion.
     new_space_.Grow();
     survived_since_last_expansion_ = 0;
   }
 }
 
 
 static bool IsUnscavengedHeapObject(Heap* heap, Object** p) {
   return heap->InNewSpace(*p) &&
@@ skipping 1013 matching lines @@
   if (!old_generation_size_configured_ && tracer()->SurvivalEventsRecorded()) {
     old_generation_allocation_limit_ =
         Max(kMinimumOldGenerationAllocationLimit,
             static_cast<intptr_t>(
                 static_cast<double>(old_generation_allocation_limit_) *
                 (tracer()->AverageSurvivalRatio() / 100)));
   }
 }
 
 
+void Heap::ConfigureNewGenerationSize() {
+  if (!new_space_high_promotion_mode_active_ &&
+      new_space_.TotalCapacity() == new_space_.MaximumCapacity() &&
+      IsStableOrIncreasingSurvivalTrend() && IsHighSurvivalRate()) {
+    // Stable high survival rates even though young generation is at
+    // maximum capacity indicates that most objects will be promoted.
+    // To decrease scavenger pauses and final mark-sweep pauses, we
+    // have to limit maximal capacity of the young generation.
+    new_space_high_promotion_mode_active_ = true;
+    if (FLAG_trace_gc) {
+      PrintPID("Limited new space size due to high promotion rate: %d MB\n",
+               new_space_.InitialTotalCapacity() / MB);
+    }
+  } else if (new_space_high_promotion_mode_active_ &&
+             IsStableOrDecreasingSurvivalTrend() && IsLowSurvivalRate()) {
+    // Decreasing low survival rates might indicate that the above high
+    // promotion mode is over and we should allow the young generation
+    // to grow again.
+    new_space_high_promotion_mode_active_ = false;
+    if (FLAG_trace_gc) {
+      PrintPID("Unlimited new space size due to low promotion rate: %d MB\n",
+               new_space_.MaximumCapacity() / MB);
+    }
+  }
+
+  if (new_space_high_promotion_mode_active_ &&
+      new_space_.TotalCapacity() > new_space_.InitialTotalCapacity()) {
+    new_space_.Shrink();
+  }
+}
+
+
 AllocationResult Heap::AllocatePartialMap(InstanceType instance_type,
                                           int instance_size) {
   Object* result = nullptr;
   AllocationResult allocation = AllocateRaw(Map::kSize, MAP_SPACE, MAP_SPACE);
   if (!allocation.To(&result)) return allocation;
 
   // Map::cast cannot be used due to uninitialized map field.
   reinterpret_cast<Map*>(result)->set_map(raw_unchecked_meta_map());
   reinterpret_cast<Map*>(result)->set_instance_type(instance_type);
   reinterpret_cast<Map*>(result)->set_instance_size(instance_size);
@@ skipping 4061 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 internal
 }  // namespace v8