7146246: G1: expose some of the -XX flags that drive which old regions to collect during mixed GCs

Summary: Make two G1 cmd line flags available in product builds: G1HeapWastePercent (previously called: G1OldReclaimableThresholdPercent) and G1MixedGCCountTarget (previous called: G1MaxMixedGCNum). Also changed the default of the former from 1% to 5% and the default for G1OldCSetRegionLiveThresholdPercent to 90%.
Reviewed-by: azeemj, jwilhelm, johnc

hotspot/src/share/vm/gc_implementation/g1/collectionSetChooser.cpp

@@ -285,7 +285,7 @@ size_t CollectionSetChooser::calcMinOldCSetLength() {
   // that the result is the same during all mixed GCs that follow a cycle.
 
   const size_t region_num = (size_t) _length;
-  const size_t gc_num = (size_t) G1MaxMixedGCNum;
+  const size_t gc_num = (size_t) G1MixedGCCountTarget;
   size_t result = region_num / gc_num;
   // emulate ceiling
   if (result * gc_num < region_num) {

hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp

@@ -2608,7 +2608,7 @@ bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
   size_t reclaimable_bytes = cset_chooser->remainingReclaimableBytes();
   size_t capacity_bytes = _g1->capacity();
   double perc = (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
-  double threshold = (double) G1OldReclaimableThresholdPercent;
+  double threshold = (double) G1HeapWastePercent;
   if (perc < threshold) {
     ergo_verbose4(ErgoMixedGCs,
               false_action_str,

hotspot/src/share/vm/gc_implementation/g1/g1_globals.hpp

@@ -299,17 +299,16 @@
           "Percentage (0-100) of the heap size to use as maximum "          \
           "young gen size.")                                                \
                                                                             \
-  develop(uintx, G1OldCSetRegionLiveThresholdPercent, 95,                   \
+  develop(uintx, G1OldCSetRegionLiveThresholdPercent, 90,                   \
           "Threshold for regions to be added to the collection set. "       \
           "Regions with more live bytes that this will not be collected.")  \
                                                                             \
-  develop(uintx, G1OldReclaimableThresholdPercent, 1,                       \
-          "Threshold for the remaining old reclaimable bytes, expressed "   \
-          "as a percentage of the heap size. If the old reclaimable bytes " \
-          "are under this we will not collect them with more mixed GCs.")   \
+  product(uintx, G1HeapWastePercent, 5,                                     \
+          "Amount of space, expressed as a percentage of the heap size, "   \
+          "that G1 is willing not to collect to avoid expensive GCs.")      \
                                                                             \
-  develop(uintx, G1MaxMixedGCNum, 4,                                        \
-          "The maximum desired number of mixed GCs after a marking cycle.") \
+  product(uintx, G1MixedGCCountTarget, 4,                                   \
+          "The target number of mixed GCs after a marking cycle.")          \
                                                                             \
   develop(uintx, G1OldCSetRegionThresholdPercent, 10,                       \
           "An upper bound for the number of old CSet regions expressed "    \