Fix the logic of when to disable the store buffer.

src/store-buffer.cc

 // Copyright 2010 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 340 matching lines @@
 
 void StoreBuffer::CheckForFullBuffer() {
   if (old_limit_ - old_top_ < kStoreBufferSize * 2) {
     // After compression we don't have enough space that we can be sure that
     // the next two compressions will have enough space in the buffer.  We
     // start by trying a more agressive compression.  If this frees up at least
     // half the space then we can keep going, otherwise it is time to brake.
     if (!during_gc_) {
       SortUniq();
     }
-    if (old_limit_ - old_top_ < old_limit_ - old_top_) {
+    if (old_limit_ - old_top_ > old_top_ - old_start_) {
       return;
     }
     // TODO(gc): Set an interrupt to do a GC on the next back edge.
     // TODO(gc): Allocate the rest of new space to force a GC on the next
     // allocation.
-    if (old_limit_ - old_top_ < kStoreBufferSize) {
-      // After compression we don't even have enough space for the next
-      // compression to be guaranteed to succeed.
-      // TODO(gc): Set a flag to scan all of memory.
-      Counters::store_buffer_overflows.Increment();
-      set_store_buffer_mode(kStoreBufferDisabled);
-    }
+    // TODO(gc): Make the disabling of the store buffer dependendent on
+    // those two measures failing:
+    // After compression not enough space was freed up in the store buffer.  We
+    // might as well stop sorting and trying to eliminate duplicates.
+    Counters::store_buffer_overflows.Increment();
+    set_store_buffer_mode(kStoreBufferDisabled);
   }
 }
 
 } }  // namespace v8::internal