--- a/hotspot/src/share/vm/gc/cms/concurrentMarkSweepGeneration.cpp	Thu Aug 06 19:52:54 2015 +0200
+++ b/hotspot/src/share/vm/gc/cms/concurrentMarkSweepGeneration.cpp	Fri Aug 07 09:15:42 2015 -0400
@@ -620,12 +620,12 @@
   // Support for parallelizing survivor space rescan
   if ((CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) || CMSParallelInitialMarkEnabled) {
     const size_t max_plab_samples =
-      ((DefNewGeneration*)_young_gen)->max_survivor_size() / plab_sample_minimum_size();
+      _young_gen->max_survivor_size() / (ThreadLocalAllocBuffer::min_size() * HeapWordSize);
 
     _survivor_plab_array  = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads, mtGC);
-    _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples, mtGC);
+    _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples, mtGC);
     _cursor               = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads, mtGC);
-    _survivor_chunk_capacity = 2*max_plab_samples;
+    _survivor_chunk_capacity = max_plab_samples;
     for (uint i = 0; i < ParallelGCThreads; i++) {
       HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples, mtGC);
       ChunkArray* cur = ::new (&_survivor_plab_array[i]) ChunkArray(vec, max_plab_samples);
@@ -641,12 +641,6 @@
   _inter_sweep_timer.start();  // start of time
 }
 
-size_t CMSCollector::plab_sample_minimum_size() {
-  // The default value of MinTLABSize is 2k, but there is
-  // no way to get the default value if the flag has been overridden.
-  return MAX2(ThreadLocalAllocBuffer::min_size() * HeapWordSize, 2 * K);
-}
-
 const char* ConcurrentMarkSweepGeneration::name() const {
   return "concurrent mark-sweep generation";
 }

--- a/hotspot/src/share/vm/gc/cms/concurrentMarkSweepGeneration.hpp	Thu Aug 06 19:52:54 2015 +0200
+++ b/hotspot/src/share/vm/gc/cms/concurrentMarkSweepGeneration.hpp	Fri Aug 07 09:15:42 2015 -0400
@@ -739,10 +739,6 @@
   size_t*    _cursor;
   ChunkArray* _survivor_plab_array;
 
-  // A bounded minimum size of PLABs, should not return too small values since
-  // this will affect the size of the data structures used for parallel young gen rescan
-  size_t plab_sample_minimum_size();
-
   // Support for marking stack overflow handling
   bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
   bool par_take_from_overflow_list(size_t num,