Tune evacuation candidate selection.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index d161b1853d8afb662193e416dfa471380f93164b..3664525c0a1d7ba7fae2b77437b34eeab15b413d 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -702,8 +702,12 @@ void MarkCompactCollector::CollectEvacuationCandidates(PagedSpace* space) {
   int candidate_count = 0;
   int total_live_bytes = 0;
 
-  bool reduce_memory =
-      heap()->ShouldReduceMemory() || heap()->HasLowAllocationRate();
+  // The minimum about of memory to make aggresive compaction worthwhile.

[Hannes Payer (out of office), 2015/10/01 14:36:07]

amount

+  const int kMinPagesToReduceMemory = 16;
+
+  bool reduce_memory = heap()->ShouldReduceMemory() ||
+                       (heap()->HasLowAllocationRate() &&

[Hannes Payer (out of office), 2015/10/01 14:36:07]

As you suggested offline, we can remove the allocation rate heuristic here.

+                        number_of_pages > kMinPageToReduceMemory);
   if (FLAG_manual_evacuation_candidates_selection) {
     for (size_t i = 0; i < pages.size(); i++) {
       Page* p = pages[i].second;