Only sweep one page eagerly unless we are running out of space.

src/spaces.h

Index: src/spaces.h
===================================================================
--- src/spaces.h	(revision 10059)
+++ src/spaces.h	(working copy)
@@ -1557,6 +1557,7 @@
   }
 
   void SetPagesToSweep(Page* first) {
+    if (first == &anchor_) first = NULL;
     first_unswept_page_ = first;
   }
 
@@ -1569,7 +1570,7 @@
   Page* FirstPage() { return anchor_.next_page(); }
   Page* LastPage() { return anchor_.prev_page(); }
 
-  bool IsFragmented(Page* p) {
+  int Fragmentation(Page* p) {

[Michael Starzinger, 2011/11/24 14:43:49]

A one-liner comment about the possible range of return values would be nice
here.

[Erik Corry, 2011/11/24 17:02:30]

Done.

     FreeList::SizeStats sizes;
     free_list_.CountFreeListItems(p, &sizes);
 
@@ -1604,8 +1605,12 @@
              (ratio > ratio_threshold) ? "[fragmented]" : "");
     }
 
-    return (ratio > ratio_threshold) ||
-        (FLAG_always_compact && sizes.Total() != Page::kObjectAreaSize);
+    if (FLAG_always_compact && sizes.Total() != Page::kObjectAreaSize) {
+      return 1;
+    }
+    if (ratio <= ratio_threshold) return 0;  // Not fragmented.
+
+    return static_cast<int>(ratio - ratio_threshold);
   }
 
   void EvictEvacuationCandidatesFromFreeLists();