Tweak compaction candidate selection to avoid keeping page with low occupancy around.

src/spaces.h

Index: src/spaces.h
diff --git a/src/spaces.h b/src/spaces.h
index 1a30078438ed74bdde507b7888b2e5a1f63ccdb4..0671b4a0b349eb063e37fef36e9fc82633375533 100644
--- a/src/spaces.h
+++ b/src/spaces.h
@@ -1589,50 +1589,8 @@ class PagedSpace : public Space {
   Page* FirstPage() { return anchor_.next_page(); }
   Page* LastPage() { return anchor_.prev_page(); }
 
-  // Returns zero for pages that have so little fragmentation that it is not
-  // worth defragmenting them.  Otherwise a positive integer that gives an
-  // estimate of fragmentation on an arbitrary scale.
-  int Fragmentation(Page* p) {
-    FreeList::SizeStats sizes;
-    free_list_.CountFreeListItems(p, &sizes);
-
-    intptr_t ratio;
-    intptr_t ratio_threshold;
-    if (identity() == CODE_SPACE) {
-      ratio = (sizes.medium_size_ * 10 + sizes.large_size_ * 2) * 100 /
-          Page::kObjectAreaSize;
-      ratio_threshold = 10;
-    } else {
-      ratio = (sizes.small_size_ * 5 + sizes.medium_size_) * 100 /
-          Page::kObjectAreaSize;
-      ratio_threshold = 15;
-    }
-
-    if (FLAG_trace_fragmentation) {
-      PrintF("%p [%d]: %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %s\n",
-             reinterpret_cast<void*>(p),
-             identity(),
-             static_cast<int>(sizes.small_size_),
-             static_cast<double>(sizes.small_size_ * 100) /
-                 Page::kObjectAreaSize,
-             static_cast<int>(sizes.medium_size_),
-             static_cast<double>(sizes.medium_size_ * 100) /
-                 Page::kObjectAreaSize,
-             static_cast<int>(sizes.large_size_),
-             static_cast<double>(sizes.large_size_ * 100) /
-                 Page::kObjectAreaSize,
-             static_cast<int>(sizes.huge_size_),
-             static_cast<double>(sizes.huge_size_ * 100) /
-                 Page::kObjectAreaSize,
-             (ratio > ratio_threshold) ? "[fragmented]" : "");
-    }
-
-    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 CountFreeListItems(Page* p, FreeList::SizeStats* sizes) {
+    free_list_.CountFreeListItems(p, sizes);
   }
 
   void EvictEvacuationCandidatesFromFreeLists();