New flag --stress-compaction

src/mark-compact.cc

 // Copyright 2011 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 415 matching lines @@
 void MarkCompactCollector::CollectEvacuationCandidates(PagedSpace* space) {
   ASSERT(space->identity() == OLD_POINTER_SPACE ||
          space->identity() == OLD_DATA_SPACE ||
          space->identity() == CODE_SPACE);
 
   PageIterator it(space);
   int count = 0;
   if (it.has_next()) it.next();  // Never compact the first page.
   while (it.has_next()) {
     Page* p = it.next();
-    if (space->IsFragmented(p)) {
+    bool evacuate = false;
+    if (FLAG_stress_compaction) {
+      int counter = space->heap()->ms_count();
+      uintptr_t page_number = reinterpret_cast<uintptr_t>(p) >> kPageSizeBits;
+      if ((counter & 1) == (page_number & 1)) evacuate = true;
+    } else {
+      if (space->IsFragmented(p)) evacuate = true;
+    }
+    if (evacuate) {
       AddEvacuationCandidate(p);
       count++;
     } else {
       p->ClearEvacuationCandidate();
     }
   }
 
   if (count > 0 && FLAG_trace_fragmentation) {
     PrintF("Collected %d evacuation candidates for space %s\n",
            count,
@@ skipping 3356 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal