Fix lazy sweeping heuristics to prevent old-space expansion.

src/mark-compact.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 3794 matching lines @@
   space->ClearStats();
 
   PageIterator it(space);
 
   intptr_t freed_bytes = 0;
   int pages_swept = 0;
   intptr_t newspace_size = space->heap()->new_space()->Size();
   bool lazy_sweeping_active = false;
   bool unused_page_present = false;
 
-  intptr_t old_space_size = heap()->PromotedSpaceSizeOfObjects();
-  intptr_t space_left =
-      Min(heap()->OldGenLimit(old_space_size, Heap::kMinPromotionLimit),
-          heap()->OldGenLimit(old_space_size, Heap::kMinAllocationLimit)) -
-      old_space_size;
-
   while (it.has_next()) {
     Page* p = it.next();
 
     // Clear sweeping flags indicating that marking bits are still intact.
     p->ClearSweptPrecisely();
     p->ClearSweptConservatively();
 
     if (p->IsEvacuationCandidate()) {
       ASSERT(evacuation_candidates_.length() > 0);
       continue;
@@ skipping 39 matching lines @@
         pages_swept++;
         break;
       }
       case LAZY_CONSERVATIVE: {
         if (FLAG_gc_verbose) {
           PrintF("Sweeping 0x%" V8PRIxPTR " conservatively as needed.\n",
                  reinterpret_cast<intptr_t>(p));
         }
         freed_bytes += SweepConservatively(space, p);
         pages_swept++;
-        if (space_left + freed_bytes > newspace_size) {
+        if (freed_bytes > 2 * newspace_size) {
           space->SetPagesToSweep(p->next_page());
           lazy_sweeping_active = true;
         } else {
           if (FLAG_gc_verbose) {
             PrintF("Only %" V8PRIdPTR " bytes freed.  Still sweeping.\n",
                    freed_bytes);
           }
         }
         break;
       }
@@ skipping 228 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal