Allocation site pretenuring.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 52711584363977303d682436a0cec6f746e7cfff..2169e51f23552fb17e107d424572feae10ea8343 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -506,7 +506,8 @@ void Heap::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;
@@ -514,7 +515,7 @@ void Heap::ProcessPretenuringFeedback() {
     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;
 
@@ -1100,12 +1101,15 @@ bool Heap::PerformGarbageCollection(GarbageCollector collector,
       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();
+      } else {
+        isolate_->stack_guard()->FullDeopt();
+      }
     }
   } else if (new_space_high_promotion_mode_active_ &&
       IsStableOrDecreasingSurvivalTrend() &&
@@ -1118,9 +1122,9 @@ bool Heap::PerformGarbageCollection(GarbageCollector collector,
       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();
     }
   }
@@ -1212,6 +1216,8 @@ 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_++;
@@ -1228,6 +1234,10 @@ void Heap::MarkCompact(GCTracer* tracer) {
   isolate_->counters()->objs_since_last_full()->Set(0);
 
   flush_monomorphic_ics_ = false;
+
+  if (FLAG_allocation_site_pretenuring) {
+    EvaluateOldSpaceLocalPretenuring(size_of_objects_before_gc);
+  }
 }
 
 
@@ -1966,6 +1976,49 @@ void Heap::ProcessAllocationSites(WeakObjectRetainer* retainer,
 }
 
 
+void Heap::ResetAllTenuredAllocationSitesDependentCode() {
+  Object* cur = allocation_sites_list();
+  while (cur->IsAllocationSite()) {
+    AllocationSite* casted = AllocationSite::cast(cur);
+    if (casted->GetPretenureMode() == TENURED) {
+      casted->ResetPretenureDecision();
+    }
+    cur = casted->weak_next();
+  }
+}
+
+
+void Heap::ResetAllAllocationSitesDependentCode() {

[mvstanton, 2014/01/09 15:33:30]

nit: ResetAllTenuredAllocationSitesDependentCode() and
ResetAllAllocationSitesDependentCode() could be the same function, accepting an
enum of ALL or TENURED.

[Hannes Payer (out of office), 2014/01/09 16:01:09]

Done. Thanks for this comment. ALL is actually not needed. When we switch on
high promotion mode, we should deopt all all code with not-tenured allocation
sites.

+  Object* cur = allocation_sites_list();
+  while (cur->IsAllocationSite()) {
+    AllocationSite* casted = AllocationSite::cast(cur);
+    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.
+    ResetAllTenuredAllocationSitesDependentCode();
+    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.