Bookkeeping for 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 69 matching lines @@
 // Will be 4 * reserved_semispace_size_ to ensure that young
 // generation can be aligned to its size.
       maximum_committed_(0),
       survived_since_last_expansion_(0),
       sweep_generation_(0),
       always_allocate_scope_depth_(0),
       linear_allocation_scope_depth_(0),
       contexts_disposed_(0),
       global_ic_age_(0),
       flush_monomorphic_ics_(false),
-      allocation_mementos_found_(0),
       scan_on_scavenge_pages_(0),
       new_space_(this),
       old_pointer_space_(NULL),
       old_data_space_(NULL),
       code_space_(NULL),
       map_space_(NULL),
       cell_space_(NULL),
       property_cell_space_(NULL),
       lo_space_(NULL),
       gc_state_(NOT_IN_GC),
@@ skipping 398 matching lines @@
   PagedSpaces spaces(this);
   for (PagedSpace* space = spaces.next();
        space != NULL;
        space = spaces.next()) {
     space->RepairFreeListsAfterBoot();
   }
 }
 
 
 void Heap::GarbageCollectionEpilogue() {
+  if (FLAG_allocation_site_pretenuring) {
+    int tenure_decisions = 0;
+    int dont_tenure_decisions = 0;
+    int allocation_mementos_found = 0;
+
+    Object* cur = allocation_sites_list();
+    if (cur->IsAllocationSite()) {

[Hannes Payer (out of office), 2013/11/25 11:45:52]

I guess the if is not needed.

[mvstanton, 2013/11/25 13:49:18]

Done.

+      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++;
+          } 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.
+
+    if (FLAG_trace_track_allocation_sites &&
+        (allocation_mementos_found > 0 ||
+         tenure_decisions > 0 ||
+         dont_tenure_decisions > 0)) {
+      PrintF("GC: (#mementos, #tenure decisions, #donttenure decisions) "
+             "(%d, %d, %d)\n",
+             allocation_mementos_found,
+             tenure_decisions,
+             dont_tenure_decisions);
+    }
+  }
+
   store_buffer()->GCEpilogue();
 
   // In release mode, we only zap the from space under heap verification.
   if (Heap::ShouldZapGarbage()) {
     ZapFromSpace();
   }
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) {
     Verify();
@@ skipping 867 matching lines @@
   }
 
  private:
   Heap* heap_;
 };
 
 
 void Heap::Scavenge() {
   RelocationLock relocation_lock(this);
 
-  allocation_mementos_found_ = 0;
-
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) VerifyNonPointerSpacePointers(this);
 #endif
 
   gc_state_ = SCAVENGE;
 
   // Implements Cheney's copying algorithm
   LOG(isolate_, ResourceEvent("scavenge", "begin"));
 
   // Clear descriptor cache.
@@ skipping 127 matching lines @@
 
   // Update how much has survived scavenge.
   IncrementYoungSurvivorsCounter(static_cast<int>(
       (PromotedSpaceSizeOfObjects() - survived_watermark) + new_space_.Size()));
 
   LOG(isolate_, ResourceEvent("scavenge", "end"));
 
   gc_state_ = NOT_IN_GC;
 
   scavenges_since_last_idle_round_++;
-
-  if (FLAG_trace_track_allocation_sites && allocation_mementos_found_ > 0) {
-    PrintF("AllocationMementos found during scavenge = %d\n",
-           allocation_mementos_found_);
-  }
 }
 
 
 String* Heap::UpdateNewSpaceReferenceInExternalStringTableEntry(Heap* heap,
                                                                 Object** p) {
   MapWord first_word = HeapObject::cast(*p)->map_word();
 
   if (!first_word.IsForwardingAddress()) {
     // Unreachable external string can be finalized.
     heap->FinalizeExternalString(String::cast(*p));
@@ skipping 2805 matching lines @@
   // space when new space is full and the object is not a large object.
   AllocationSpace retry_space =
       (space != NEW_SPACE) ? space : TargetSpaceId(map->instance_type());
   int size = map->instance_size() + AllocationMemento::kSize;
   Object* result;
   MaybeObject* maybe_result = AllocateRaw(size, space, retry_space);
   if (!maybe_result->ToObject(&result)) return maybe_result;
   // No need for write barrier since object is white and map is in old space.
   HeapObject::cast(result)->set_map_no_write_barrier(map);
   AllocationMemento* alloc_memento = reinterpret_cast<AllocationMemento*>(
       reinterpret_cast<Address>(result) + map->instance_size());

[Hannes Payer (out of office), 2013/11/25 11:45:52]

Is there a way to increase the memento count at memento creation time? Right now
it seems to be a bit fragile to manually increase the counter after creating the
memento.

[mvstanton, 2013/11/25 13:49:18]

I consolidated the two heap.cc memento construction sites in
InitializeAllocationMemento, so there is some encapsulation. The remaining site
that creates a memento is in HGraphBuilder::BuildJSArrayHeader(). Obviously the
method is different (hydrogen nodes).

BTW, you prompted me to go look at BuildJSArrayHeader() and I found that I
wasn't skipping an overflow check that I should, so I fixed that. I definitely
don't want a HeapNumber in the memento count field!

   alloc_memento->set_map_no_write_barrier(allocation_memento_map());
   ASSERT(allocation_site->map() == allocation_site_map());
   alloc_memento->set_allocation_site(*allocation_site, SKIP_WRITE_BARRIER);
+  if (FLAG_allocation_site_pretenuring) {
+    allocation_site->IncrementMementoCreateCount();
+  }
   return result;
 }
 
 
 MaybeObject* Heap::Allocate(Map* map, AllocationSpace space) {
   ASSERT(gc_state_ == NOT_IN_GC);
   ASSERT(map->instance_type() != MAP_TYPE);
   // If allocation failures are disallowed, we may allocate in a different
   // space when new space is full and the object is not a large object.
   AllocationSpace retry_space =
@@ skipping 412 matching lines @@
 MaybeObject* Heap::CopyJSObject(JSObject* source, AllocationSite* site) {
   // Never used to copy functions.  If functions need to be copied we
   // have to be careful to clear the literals array.
   SLOW_ASSERT(!source->IsJSFunction());
 
   // Make the clone.
   Map* map = source->map();
   int object_size = map->instance_size();
   Object* clone;
 
-  ASSERT(site == NULL || (AllocationSite::CanTrack(map->instance_type()) &&
-                          map->instance_type() == JS_ARRAY_TYPE));
+  ASSERT(site == NULL || AllocationSite::CanTrack(map->instance_type()));
 
   WriteBarrierMode wb_mode = UPDATE_WRITE_BARRIER;
 
   // If we're forced to always allocate, we use the general allocation
   // functions which may leave us with an object in old space.
   if (always_allocate()) {
     { MaybeObject* maybe_clone =
           AllocateRaw(object_size, NEW_SPACE, OLD_POINTER_SPACE);
       if (!maybe_clone->ToObject(&clone)) return maybe_clone;
     }
@@ skipping 21 matching lines @@
     CopyBlock(HeapObject::cast(clone)->address(),
               source->address(),
               object_size);
 
     if (site != NULL) {
       AllocationMemento* alloc_memento = reinterpret_cast<AllocationMemento*>(
           reinterpret_cast<Address>(clone) + object_size);
       alloc_memento->set_map_no_write_barrier(allocation_memento_map());
       ASSERT(site->map() == allocation_site_map());
       alloc_memento->set_allocation_site(site, SKIP_WRITE_BARRIER);
+      if (FLAG_allocation_site_pretenuring) {
+        site->IncrementMementoCreateCount();
+      }
       HeapProfiler* profiler = isolate()->heap_profiler();
       if (profiler->is_tracking_allocations()) {
         profiler->UpdateObjectSizeEvent(HeapObject::cast(clone)->address(),
                                         object_size);
         profiler->NewObjectEvent(alloc_memento->address(),
                                  AllocationMemento::kSize);
       }
     }
   }
 
@@ skipping 3091 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