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6684579: SoftReference processing can be made more efficient

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For current soft-ref clearing policies, we can decide at marking time if a soft-reference will definitely not be cleared, postponing the decision of whether it will definitely be cleared to the final reference processing phase. This can be especially beneficial in the case of concurrent collectors where the marking is usually concurrent but reference processing is usually not.

Reviewed-by: jmasa
This commit is contained in:
Y. Srinivas Ramakrishna 2008-11-20 16:56:09 -08:00
parent db6bef2c70
commit 7d7cf3f8af
18 changed files with 137 additions and 164 deletions
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45
hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp
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@ -1961,6 +1961,7 @@ void CMSCollector::do_compaction_work(bool clear_all_soft_refs) {
ref_processor()->set_enqueuing_is_done(false);
ref_processor()->enable_discovery();
ref_processor()->snap_policy(clear_all_soft_refs);
// If an asynchronous collection finishes, the _modUnionTable is
// all clear. If we are assuming the collection from an asynchronous
// collection, clear the _modUnionTable.
@ -2384,6 +2385,9 @@ void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) {
Universe::verify(true);
}
// Snapshot the soft reference policy to be used in this collection cycle.
ref_processor()->snap_policy(clear_all_soft_refs);
bool init_mark_was_synchronous = false; // until proven otherwise
while (_collectorState != Idling) {
if (TraceCMSState) {
@ -4591,11 +4595,11 @@ size_t CMSCollector::preclean_mod_union_table(
if (!dirtyRegion.is_empty()) {
assert(numDirtyCards > 0, "consistency check");
HeapWord* stop_point = NULL;
stopTimer();
CMSTokenSyncWithLocks ts(true, gen->freelistLock(),
bitMapLock());
startTimer();
{
stopTimer();
CMSTokenSyncWithLocks ts(true, gen->freelistLock(),
bitMapLock());
startTimer();
verify_work_stacks_empty();
verify_overflow_empty();
sample_eden();
@ -4612,10 +4616,6 @@ size_t CMSCollector::preclean_mod_union_table(
assert((CMSPermGenPrecleaningEnabled && (gen == _permGen)) ||
(_collectorState == AbortablePreclean && should_abort_preclean()),
"Unparsable objects should only be in perm gen.");
stopTimer();
CMSTokenSyncWithLocks ts(true, bitMapLock());
startTimer();
_modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end()));
if (should_abort_preclean()) {
break; // out of preclean loop
@ -5678,23 +5678,14 @@ void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) {
ResourceMark rm;
HandleMark hm;
ReferencePolicy* soft_ref_policy;
assert(!ref_processor()->enqueuing_is_done(), "Enqueuing should not be complete");
// Process weak references.
if (clear_all_soft_refs) {
soft_ref_policy = new AlwaysClearPolicy();
} else {
#ifdef COMPILER2
soft_ref_policy = new LRUMaxHeapPolicy();
#else
soft_ref_policy = new LRUCurrentHeapPolicy();
#endif // COMPILER2
}
verify_work_stacks_empty();
ReferenceProcessor* rp = ref_processor();
assert(rp->span().equals(_span), "Spans should be equal");
assert(!rp->enqueuing_is_done(), "Enqueuing should not be complete");
// Process weak references.
rp->snap_policy(clear_all_soft_refs);
verify_work_stacks_empty();
CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap,
&_markStack, false /* !preclean */);
CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this,
@ -5704,14 +5695,12 @@ void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) {
TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty);
if (rp->processing_is_mt()) {
CMSRefProcTaskExecutor task_executor(*this);
rp->process_discovered_references(soft_ref_policy,
&_is_alive_closure,
rp->process_discovered_references(&_is_alive_closure,
&cmsKeepAliveClosure,
&cmsDrainMarkingStackClosure,
&task_executor);
} else {
rp->process_discovered_references(soft_ref_policy,
&_is_alive_closure,
rp->process_discovered_references(&_is_alive_closure,
&cmsKeepAliveClosure,
&cmsDrainMarkingStackClosure,
NULL);
@ -6166,8 +6155,8 @@ void CMSCollector::verify_ok_to_terminate() const {
#endif
size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const {
assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1),
"missing Printezis mark?");
assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1),
"missing Printezis mark?");
HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2);
size_t size = pointer_delta(nextOneAddr + 1, addr);
assert(size == CompactibleFreeListSpace::adjustObjectSize(size),