store the "default size" for the PLAB in the PLABStats

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -1406,8 +1406,8 @@ G1CollectedHeap::G1CollectedHeap() :
   _summary_bytes_used(0),
   _bytes_used_during_gc(0),
   _archive_allocator(NULL),
-  _survivor_evac_stats("Young", YoungPLABSize * ParallelGCThreads, PLABWeight),
-  _old_evac_stats("Old", OldPLABSize * ParallelGCThreads, PLABWeight),
+  _survivor_evac_stats("Young", YoungPLABSize, YoungPLABSize * ParallelGCThreads, PLABWeight),
+  _old_evac_stats("Old", OldPLABSize, OldPLABSize * ParallelGCThreads, PLABWeight),
   _expand_heap_after_alloc_failure(true),
   _g1mm(NULL),
   _humongous_reclaim_candidates(),

src/hotspot/share/gc/g1/g1EvacStats.cpp

@@ -88,8 +88,8 @@ size_t G1EvacStats::compute_desired_plab_sz() {
   return cur_plab_sz;
 }
 
-G1EvacStats::G1EvacStats(const char* description, size_t desired_plab_sz_, unsigned wt) :
-  PLABStats(description, desired_plab_sz_, wt),
+G1EvacStats::G1EvacStats(const char* description, size_t default_plab_sz, size_t desired_plab_sz_, unsigned wt) :
+  PLABStats(description, default_plab_sz, desired_plab_sz_, wt), // desired_plab_size should be the total PLAB size for all threads.
   _region_end_waste(0),
   _regions_filled(0),
   _direct_allocated(0),

src/hotspot/share/gc/g1/g1EvacStats.hpp

@@ -56,7 +56,7 @@ class G1EvacStats : public PLABStats {
   virtual size_t compute_desired_plab_sz();
 
  public:
-  G1EvacStats(const char* description, size_t desired_plab_sz_, unsigned wt);
+  G1EvacStats(const char* description, size_t default_plab_sz, size_t desired_plab_sz_, unsigned wt);
 
   ~G1EvacStats();
 

src/hotspot/share/gc/shared/plab.cpp

@@ -135,6 +135,9 @@ void PLABStats::log_sizing(size_t calculated_words, size_t net_desired_words) {
 
 // Calculates plab size for current number of gc worker threads.
 size_t PLABStats::desired_plab_sz(uint no_of_gc_workers) {
+  if (!ResizePLAB) {
+      return _default_plab_sz;
+  }
   return align_object_size(clamp(_desired_net_plab_sz / no_of_gc_workers, min_size(), max_size()));
 }
 

src/hotspot/share/gc/shared/plab.hpp

@@ -151,6 +151,7 @@ class PLABStats : public CHeapObj<mtGC> {
   size_t _wasted;             // of which wasted (internal fragmentation)
   size_t _undo_wasted;        // of which wasted on undo (is not used for calculation of PLAB size)
   size_t _unused;             // Unused in last buffer
+  size_t _default_plab_sz;
   size_t _desired_net_plab_sz;// Output of filter (below), suitably trimmed and quantized
   AdaptiveWeightedAverage
          _filter;             // Integrator with decay
@@ -169,12 +170,13 @@ class PLABStats : public CHeapObj<mtGC> {
   virtual size_t compute_desired_plab_sz();
 
  public:
-  PLABStats(const char* description, size_t desired_net_plab_sz_, unsigned wt) :
+  PLABStats(const char* description, size_t default_plab_sz, size_t desired_net_plab_sz_, unsigned wt) :
     _description(description),
     _allocated(0),
     _wasted(0),
     _undo_wasted(0),
     _unused(0),
+    _default_plab_sz(default_plab_sz),
     _desired_net_plab_sz(desired_net_plab_sz_),
     _filter(wt)
   { }