Tenure allocation sites only when semi-space is maximum size.

src/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 "v8.h"
 
 #include "accessors.h"
 #include "api.h"
 #include "bootstrapper.h"
 #include "codegen.h"
@@ skipping 83 matching lines @@
       store_buffer_rebuilder_(store_buffer()),
       hidden_string_(NULL),
       gc_safe_size_of_old_object_(NULL),
       total_regexp_code_generated_(0),
       tracer_(NULL),
       high_survival_rate_period_length_(0),
       promoted_objects_size_(0),
       promotion_rate_(0),
       semi_space_copied_object_size_(0),
       semi_space_copied_rate_(0),
+      changed_to_max_semi_space_size_(false),
       max_gc_pause_(0.0),
       total_gc_time_ms_(0.0),
       max_alive_after_gc_(0),
       min_in_mutator_(kMaxInt),
       alive_after_last_gc_(0),
       last_gc_end_timestamp_(0.0),
       marking_time_(0.0),
       sweeping_time_(0.0),
       mark_compact_collector_(this),
       store_buffer_(this),
@@ skipping 317 matching lines @@
   if (FLAG_gc_verbose) Print();
 
   ReportStatisticsBeforeGC();
 #endif  // DEBUG
 
   store_buffer()->GCPrologue();
 
   if (isolate()->concurrent_osr_enabled()) {
     isolate()->optimizing_compiler_thread()->AgeBufferedOsrJobs();
   }
+
+  CheckNewSpaceExpansionCriteria();
 }
 
 
 intptr_t Heap::SizeOfObjects() {
   intptr_t total = 0;
   AllSpaces spaces(this);
   for (Space* space = spaces.next(); space != NULL; space = spaces.next()) {
     total += space->SizeOfObjects();
   }
   return total;
@@ skipping 27 matching lines @@
 void Heap::ProcessPretenuringFeedback() {
   if (FLAG_allocation_site_pretenuring) {
     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
     // sites list.
+    // TODO(hpayer): We iterate over the whole list of allocation sites when
+    // we grew to the maximum semi-space size to deopt maybe tenured
+    // allocation sites. We could hold the maybe tenured allocation sites
+    // in a seperate data structure if this is a performance problem.
     bool use_scratchpad =
-        allocation_sites_scratchpad_length_ < kAllocationSiteScratchpadSize;
+        allocation_sites_scratchpad_length_ < kAllocationSiteScratchpadSize &&
+        !changed_to_max_semi_space_size_;
 
     int i = 0;
     Object* list_element = allocation_sites_list();
     bool trigger_deoptimization = false;
     while (use_scratchpad ?
               i < allocation_sites_scratchpad_length_ :
               list_element->IsAllocationSite()) {
       AllocationSite* site = use_scratchpad ?
           AllocationSite::cast(allocation_sites_scratchpad()->get(i)) :
           AllocationSite::cast(list_element);
       allocation_mementos_found += site->memento_found_count();
       if (site->memento_found_count() > 0) {
         active_allocation_sites++;
+        if (site->DigestPretenuringFeedback()) trigger_deoptimization = true;
+        if (site->GetPretenureMode() == TENURED) {
+          tenure_decisions++;
+        } else {
+          dont_tenure_decisions++;
+        }
+        allocation_sites++;
       }
-      if (site->DigestPretenuringFeedback()) trigger_deoptimization = true;
-      if (site->GetPretenureMode() == TENURED) {
-        tenure_decisions++;
-      } else {
-        dont_tenure_decisions++;
-      }
-      allocation_sites++;
+
       if (use_scratchpad) {
         i++;
       } else {
         list_element = site->weak_next();
       }
     }
 
     if (trigger_deoptimization) {
       isolate_->stack_guard()->RequestDeoptMarkedAllocationSites();
     }
@@ skipping 755 matching lines @@
     HeapObjectIterator data_it(heap->old_data_space());
     for (HeapObject* object = data_it.Next();
          object != NULL; object = data_it.Next())
       object->Iterate(&v);
   }
 }
 #endif  // VERIFY_HEAP
 
 
 void Heap::CheckNewSpaceExpansionCriteria() {
+  changed_to_max_semi_space_size_ = false;
   if (new_space_.Capacity() < new_space_.MaximumCapacity() &&
       survived_since_last_expansion_ > new_space_.Capacity()) {
     // Grow the size of new space if there is room to grow, enough data
     // has survived scavenge since the last expansion and we are not in
     // high promotion mode.
     new_space_.Grow();
     survived_since_last_expansion_ = 0;
+    if (new_space_.IsAtMaximumCapacity()) {
+      changed_to_max_semi_space_size_ = true;

[mvstanton, 2014/06/02 13:31:25]

Is the boolean really needed? Why not just ask new_space_.IsAtMaximumCapacity().
I'm thinking it might be some redundant/duplicate state.

[Hannes Payer (out of office), 2014/06/02 14:56:52]

As discussed offline, we need a separate flag to identify valid pretenuring
feedback

+    }
   }
 }
 
 
 static bool IsUnscavengedHeapObject(Heap* heap, Object** p) {
   return heap->InNewSpace(*p) &&
       !HeapObject::cast(*p)->map_word().IsForwardingAddress();
 }
 
 
@@ skipping 123 matching lines @@
 
   // Implements Cheney's copying algorithm
   LOG(isolate_, ResourceEvent("scavenge", "begin"));
 
   // Clear descriptor cache.
   isolate_->descriptor_lookup_cache()->Clear();
 
   // Used for updating survived_since_last_expansion_ at function end.
   intptr_t survived_watermark = PromotedSpaceSizeOfObjects();
 
-  CheckNewSpaceExpansionCriteria();
-
   SelectScavengingVisitorsTable();
 
   incremental_marking()->PrepareForScavenge();
 
   // Flip the semispaces.  After flipping, to space is empty, from space has
   // live objects.
   new_space_.Flip();
   new_space_.ResetAllocationInfo();
 
   // We need to sweep newly copied objects which can be either in the
@@ skipping 4969 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
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal