Allow main thread to contribute to the sweeping phase.

src/spaces.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/v8.h"
 
 #include "src/base/platform/platform.h"
 #include "src/full-codegen.h"
 #include "src/macro-assembler.h"
 #include "src/mark-compact.h"
@@ skipping 2563 matching lines @@
     int remaining =
         static_cast<int>(allocation_info_.limit() - allocation_info_.top());
     heap()->CreateFillerObjectAt(allocation_info_.top(), remaining);
 
     allocation_info_.set_top(NULL);
     allocation_info_.set_limit(NULL);
   }
 }
 
 
 HeapObject* PagedSpace::WaitForSweeperThreadsAndRetryAllocation(

[Jarin, 2014/07/09 11:02:02]

Nit: Now the name is a bit funny - it does not always wait for the sweeper
threads.

[Hannes Payer (out of office), 2014/07/10 12:03:45]

Done.

     int size_in_bytes) {
   MarkCompactCollector* collector = heap()->mark_compact_collector();
 
-  // If sweeper threads are still running, wait for them.
   if (collector->IsConcurrentSweepingInProgress(this)) {
+    // If sweeping is still in progress try to sweep pages on the main thread.
+    int free_chunk =
+        collector->SweepInParallel<MarkCompactCollector::SWEEP_ON_MAIN_THREAD>(
+            this, size_in_bytes);
+    if (free_chunk >= size_in_bytes) {
+      HeapObject* object = free_list_.Allocate(size_in_bytes);
+      // We should be able to allocate an object here since we just freed that
+      // much memory.
+      ASSERT(object != NULL);
+      if (object != NULL) return object;
+    }
+
+    // Wait for the sweeper threads here and complete the sweeping phase.
     collector->WaitUntilSweepingCompleted();
 
     // After waiting for the sweeper threads, there may be new free-list
     // entries.
     return free_list_.Allocate(size_in_bytes);
   }
   return NULL;
 }
 
 
@@ skipping 541 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal