[heap] Remove store_buffer_counter from MemoryChunk

src/heap/store-buffer.cc

 // Copyright 2011 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 "src/heap/store-buffer.h"
 
 #include <algorithm>
 
 #include "src/counters.h"
 #include "src/heap/incremental-marking.h"
@@ skipping 164 matching lines @@
     DCHECK(i != (kSampleFinenesses - 1) || old_top_ == old_start_);
     if (SpaceAvailable(space_needed)) return;
   }
   UNREACHABLE();
 }
 
 
 // Sample the store buffer to see if some pages are taking up a lot of space
 // in the store buffer.
 void StoreBuffer::ExemptPopularPages(int prime_sample_step, int threshold) {
-  PointerChunkIterator it(heap_);
-  MemoryChunk* chunk;
-  while ((chunk = it.next()) != NULL) {
-    chunk->set_store_buffer_counter(0);
-  }
+  HashMap store_buffer_counts(HashMap::PointersMatch, 16);
   bool created_new_scan_on_scavenge_pages = false;
   MemoryChunk* previous_chunk = NULL;
   for (Address* p = old_start_; p < old_top_; p += prime_sample_step) {
     Address addr = *p;
     MemoryChunk* containing_chunk = NULL;
     if (previous_chunk != NULL && previous_chunk->Contains(addr)) {
       containing_chunk = previous_chunk;
     } else {
       containing_chunk = MemoryChunk::FromAnyPointerAddress(heap_, addr);
     }
-    int old_counter = containing_chunk->store_buffer_counter();
+    HashMap::Entry* e = store_buffer_counts.LookupOrInsert(
+        containing_chunk,
+        static_cast<uint32_t>(reinterpret_cast<uintptr_t>(containing_chunk) >>
+                              kPageSizeBits));
+    intptr_t old_counter = bit_cast<intptr_t>(e->value);
     if (old_counter >= threshold) {
       containing_chunk->set_scan_on_scavenge(true);
       created_new_scan_on_scavenge_pages = true;
     }
-    containing_chunk->set_store_buffer_counter(old_counter + 1);
+    (*bit_cast<intptr_t*>(&e->value))++;
     previous_chunk = containing_chunk;
   }
   if (created_new_scan_on_scavenge_pages) {
     Filter(MemoryChunk::SCAN_ON_SCAVENGE);
     heap_->isolate()->CountUsage(
         v8::Isolate::UseCounterFeature::kStoreBufferOverflow);
   }
   old_buffer_is_filtered_ = true;
 }
 
@@ skipping 399 matching lines @@
       DCHECK(start_of_current_page_ != store_buffer_->Top());
       store_buffer_->SetTop(start_of_current_page_);
     }
   } else {
     UNREACHABLE();
   }
 }
 
 }  // namespace internal
 }  // namespace v8