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6593758: RFE: Enhance GC ergonomics to dynamically choose ParallelGCThreads

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Select number of GC threads dynamically based on heap usage and number of Java threads

Reviewed-by: johnc, ysr, jcoomes
This commit is contained in:
Jon Masamitsu 2011-08-09 10:16:01 -07:00
parent 098ed89645
commit 15070123fa
39 changed files with 1523 additions and 231 deletions
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18
hotspot/src/share/vm/gc_implementation/g1/collectionSetChooser.cpp
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@ -255,7 +255,18 @@ void
CollectionSetChooser::
prepareForAddMarkedHeapRegionsPar(size_t n_regions, size_t chunkSize) {
_first_par_unreserved_idx = 0;
size_t max_waste = ParallelGCThreads * chunkSize;
int n_threads = ParallelGCThreads;
if (UseDynamicNumberOfGCThreads) {
assert(G1CollectedHeap::heap()->workers()->active_workers() > 0,
"Should have been set earlier");
// This is defensive code. As the assertion above says, the number
// of active threads should be > 0, but in case there is some path
// or some improperly initialized variable with leads to no
// active threads, protect against that in a product build.
n_threads = MAX2(G1CollectedHeap::heap()->workers()->active_workers(),
1);
}
size_t max_waste = n_threads * chunkSize;
// it should be aligned with respect to chunkSize
size_t aligned_n_regions =
(n_regions + (chunkSize - 1)) / chunkSize * chunkSize;
@ -265,6 +276,11 @@ prepareForAddMarkedHeapRegionsPar(size_t n_regions, size_t chunkSize) {
jint
CollectionSetChooser::getParMarkedHeapRegionChunk(jint n_regions) {
// Don't do this assert because this can be called at a point
// where the loop up stream will not execute again but might
// try to claim more chunks (loop test has not been done yet).
// assert(_markedRegions.length() > _first_par_unreserved_idx,
// "Striding beyond the marked regions");
jint res = Atomic::add(n_regions, &_first_par_unreserved_idx);
assert(_markedRegions.length() > res + n_regions - 1,
"Should already have been expanded");