Limit shrinkage: allow growth by at least half the pages freed by GC.

runtime/vm/pages.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 685 matching lines @@
         after_total_in_words /  desired_utilization_);
     intptr_t capacity_growth_in_words =
       Utils::RoundUp(Utils::Maximum(static_cast<intptr_t>(0),
                                     used_target - after.capacity_in_words),
                        PageSpace::kPageSizeInWords);
     int capacity_growth_in_pages =
         capacity_growth_in_words / PageSpace::kPageSizeInWords;
     grow_heap_ = Utils::Maximum(capacity_growth_in_pages, heap_growth_rate_);
     heap->RecordData(PageSpace::kPageGrowth, capacity_growth_in_pages);
   }
+  // Limit shrinkage: allow growth by at least half the pages freed by GC.
+  intptr_t freed_pages =
+      (before.capacity_in_words - after.capacity_in_words) /
+      PageSpace::kPageSizeInWords;
+  grow_heap_ = Utils::Maximum(grow_heap_, freed_pages / 2);
   heap->RecordData(PageSpace::kGarbageRatio, collected_garbage_ratio);
   heap->RecordData(PageSpace::kGCTimeFraction,
                    garbage_collection_time_fraction);
   heap->RecordData(PageSpace::kAllowedGrowth, grow_heap_);
   last_usage_ = after;
 }
 
 
 PageSpaceGarbageCollectionHistory::PageSpaceGarbageCollectionHistory()
     : index_(0) {
@@ skipping 32 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result= static_cast<int>((static_cast<double>(gc_time) /
                              static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart