Allocation site pretenuring.

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // 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 499 matching lines @@
     int dont_tenure_decisions = 0;
     int allocation_mementos_found = 0;
 
     Object* cur = allocation_sites_list();
     while (cur->IsAllocationSite()) {
       AllocationSite* casted = AllocationSite::cast(cur);
       allocation_mementos_found += casted->memento_found_count()->value();
       if (casted->DigestPretenuringFeedback()) {
         if (casted->GetPretenureMode() == TENURED) {
           tenure_decisions++;
+          casted->dependent_code()->DeoptimizeDependentCodeGroup(

[Michael Starzinger, 2013/12/02 15:12:54]

IMHO this should be done as part of DigestPretenuringFeedback() instead of here.
Also we need to deopt whenever the decision changes in either way, not just when
we switch from NOT_TENURED to TENURED I think.

[Hannes Payer (out of office), 2014/01/09 14:37:13]

Done.

+              isolate_,
+              DependentCode::kAllocationSiteTenuringChangedGroup);
         } else {
           dont_tenure_decisions++;
         }
       }
       cur = casted->weak_next();
     }
 
     // TODO(mvstanton): Pretenure decisions are only made once for an allocation
     // site. Find a sane way to decide about revisiting the decision later.
 
@@ skipping 535 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.
-    if (FLAG_pretenuring) {
-      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
-    // possible.
-    if (FLAG_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);
 
   // Callbacks that fire after this point might trigger nested GCs and
@@ skipping 69 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;
+
+  EvaluateLocalPretenuring(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 719 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::ClearAllAllocationSitesDependentCode() {
+  Object* cur = allocation_sites_list();
+  while (cur->IsAllocationSite()) {
+    AllocationSite* casted = AllocationSite::cast(cur);
+    casted->ResetPretenureDecision();
+    cur = casted->weak_next();
+  }
+}
+
+
+void Heap::EvaluateLocalPretenuring(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.
+    ClearAllAllocationSitesDependentCode();
+    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;
 
   // Both the external string table and the string table may contain
   // external strings, but neither lists them exhaustively, nor is the
   // intersection set empty.  Therefore we iterate over the external string
   // table first, ignoring internalized strings, and then over the
   // internalized string table.
 
   class ExternalStringTableVisitorAdapter : public ObjectVisitor {
@@ skipping 6036 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