Allocation site pretenuring.

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 488 matching lines @@
   PagedSpaces spaces(this);
   for (PagedSpace* space = spaces.next();
        space != NULL;
        space = spaces.next()) {
     space->RepairFreeListsAfterBoot();
   }
 }
 
 
 void Heap::ProcessPretenuringFeedback() {
-  if (FLAG_allocation_site_pretenuring) {
+  if (FLAG_allocation_site_pretenuring &&
+      new_space_high_promotion_mode_active_) {
     int tenure_decisions = 0;
     int dont_tenure_decisions = 0;
     int allocation_mementos_found = 0;
     int allocation_sites = 0;
     int active_allocation_sites = 0;
 
     // If the scratchpad overflowed, we have to iterate over the allocation
-    // stites list.
+    // sites list.
     bool use_scratchpad =
         allocation_sites_scratchpad_length < kAllocationSiteScratchpadSize;
 
     int i = 0;
     Object* list_element = allocation_sites_list();
     while (use_scratchpad ?
               i < allocation_sites_scratchpad_length :
               list_element->IsAllocationSite()) {
       AllocationSite* site = use_scratchpad ?
         allocation_sites_scratchpad[i] : AllocationSite::cast(list_element);
@@ skipping 565 matching lines @@
       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.
     SetNewSpaceHighPromotionModeActive(true);
     if (FLAG_trace_gc) {
       PrintPID("Limited new space size due to high promotion rate: %d MB\n",
                new_space_.InitialCapacity() / MB);
     }
-    // Support for global pre-tenuring uses the high promotion mode as a
-    // heuristic indicator of whether to pretenure or not, we trigger
-    // deoptimization here to take advantage of pre-tenuring as soon as
-    // possible.
+    // The high promotion mode is our indicator to turn on pretenuring. We have
+    // to deoptimize all optimized code in global pretenuring mode and all
+    // code which should be tenured in local pretenuring mode.
     if (FLAG_pretenuring) {
-      isolate_->stack_guard()->FullDeopt();
+      if (FLAG_allocation_site_pretenuring) {
+        ResetAllAllocationSitesDependentCode(NOT_TENURED);
+      } else {
+        isolate_->stack_guard()->FullDeopt();
+      }
     }
   } 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.
     SetNewSpaceHighPromotionModeActive(false);
     if (FLAG_trace_gc) {
       PrintPID("Unlimited new space size due to low promotion rate: %d MB\n",
                new_space_.MaximumCapacity() / MB);
     }
-    // Trigger deoptimization here to turn off pre-tenuring as soon as
+    // Trigger deoptimization here to turn off global pretenuring as soon as
     // possible.
-    if (FLAG_pretenuring) {
+    if (FLAG_pretenuring && !FLAG_allocation_site_pretenuring) {
       isolate_->stack_guard()->FullDeopt();
     }
   }
 
   if (new_space_high_promotion_mode_active_ &&
       new_space_.Capacity() > new_space_.InitialCapacity()) {
     new_space_.Shrink();
   }
 
   isolate_->counters()->objs_since_last_young()->Set(0);
@@ skipping 71 matching lines @@
       }
     }
   }
 }
 
 
 void Heap::MarkCompact(GCTracer* tracer) {
   gc_state_ = MARK_COMPACT;
   LOG(isolate_, ResourceEvent("markcompact", "begin"));
 
+  uint64_t size_of_objects_before_gc = SizeOfObjects();
+
   mark_compact_collector_.Prepare(tracer);
 
   ms_count_++;
   tracer->set_full_gc_count(ms_count_);
 
   MarkCompactPrologue();
 
   mark_compact_collector_.CollectGarbage();
 
   LOG(isolate_, ResourceEvent("markcompact", "end"));
 
   gc_state_ = NOT_IN_GC;
 
   isolate_->counters()->objs_since_last_full()->Set(0);
 
   flush_monomorphic_ics_ = false;
+
+  if (FLAG_allocation_site_pretenuring) {
+    EvaluateOldSpaceLocalPretenuring(size_of_objects_before_gc);
+  }
 }
 
 
 void Heap::MarkCompactPrologue() {
   // At any old GC clear the keyed lookup cache to enable collection of unused
   // maps.
   isolate_->keyed_lookup_cache()->Clear();
   isolate_->context_slot_cache()->Clear();
   isolate_->descriptor_lookup_cache()->Clear();
   RegExpResultsCache::Clear(string_split_cache());
@@ skipping 718 matching lines @@
 void Heap::ProcessAllocationSites(WeakObjectRetainer* retainer,
                                   bool record_slots) {
   Object* allocation_site_obj =
       VisitWeakList<AllocationSite>(this,
                                     allocation_sites_list(),
                                     retainer, record_slots);
   set_allocation_sites_list(allocation_site_obj);
 }
 
 
+void Heap::ResetAllAllocationSitesDependentCode(PretenureFlag flag) {
+  Object* cur = allocation_sites_list();
+  while (cur->IsAllocationSite()) {
+    AllocationSite* casted = AllocationSite::cast(cur);
+    if (casted->GetPretenureMode() == flag) {
+      casted->ResetPretenureDecision();
+    }
+    cur = casted->weak_next();
+  }
+}
+
+
+void Heap::EvaluateOldSpaceLocalPretenuring(
+    uint64_t size_of_objects_before_gc) {
+  uint64_t size_of_objects_after_gc = SizeOfObjects();
+  double old_generation_survival_rate =
+      (static_cast<double>(size_of_objects_after_gc) * 100) /
+          static_cast<double>(size_of_objects_before_gc);
+
+  if (old_generation_survival_rate < kOldSurvivalRateLowThreshold) {
+    // Too many objects died in the old generation, pretenuring of wrong
+    // allocation sites may be the cause for that. We have to deopt all
+    // dependent code registered in the allocation sites to re-evaluate
+    // our pretenuring decisions.
+    ResetAllAllocationSitesDependentCode(TENURED);
+    if (FLAG_trace_pretenuring) {
+      PrintF("Deopt all allocation sites dependent code due to low survival "
+             "rate in the old generation %f\n", old_generation_survival_rate);
+    }
+  }
+}
+
+
 void Heap::VisitExternalResources(v8::ExternalResourceVisitor* visitor) {
   DisallowHeapAllocation no_allocation;
   // All external strings are listed in the external string table.
 
   class ExternalStringTableVisitorAdapter : public ObjectVisitor {
    public:
     explicit ExternalStringTableVisitorAdapter(
         v8::ExternalResourceVisitor* visitor) : visitor_(visitor) {}
     virtual void VisitPointers(Object** start, Object** end) {
       for (Object** p = start; p < end; p++) {
@@ skipping 5756 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   OS::MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   OS::MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal