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

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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
This commit is contained in:
Antonios Printezis 2012-03-23 10:53:19 -04:00
parent 006def0451
commit 450d6e8d9a
3 changed files with 8 additions and 9 deletions
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2
hotspot/src/share/vm/gc_implementation/g1/collectionSetChooser.cpp
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@ -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) {

2
hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp
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@ -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,

13
hotspot/src/share/vm/gc_implementation/g1/g1_globals.hpp
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@ -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 " \