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7037276: Unnecessary double traversal of dirty card windows

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Short-circuited an unnecessary double traversal of dirty card windows when iterating younger refs. Also renamed some cardtable methods for more clarity.

Reviewed-by: jmasa, stefank, poonam
This commit is contained in:
Y. Srinivas Ramakrishna 2011-04-20 19:19:30 -07:00
parent 12d1d9acc1
commit b4d40650b2
5 changed files with 198 additions and 162 deletions
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32
hotspot/src/share/vm/memory/cardTableModRefBS.cpp
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@ -456,31 +456,35 @@ bool CardTableModRefBS::mark_card_deferred(size_t card_index) {
}
void CardTableModRefBS::non_clean_card_iterate(Space* sp,
MemRegion mr,
DirtyCardToOopClosure* dcto_cl,
MemRegionClosure* cl) {
void CardTableModRefBS::non_clean_card_iterate_possibly_parallel(Space* sp,
MemRegion mr,
DirtyCardToOopClosure* dcto_cl,
ClearNoncleanCardWrapper* cl) {
if (!mr.is_empty()) {
int n_threads = SharedHeap::heap()->n_par_threads();
if (n_threads > 0) {
#ifndef SERIALGC
par_non_clean_card_iterate_work(sp, mr, dcto_cl, cl, n_threads);
non_clean_card_iterate_parallel_work(sp, mr, dcto_cl, cl, n_threads);
#else // SERIALGC
fatal("Parallel gc not supported here.");
#endif // SERIALGC
} else {
non_clean_card_iterate_work(mr, cl);
// We do not call the non_clean_card_iterate_serial() version below because
// we want to clear the cards (which non_clean_card_iterate_serial() does not
// do for us), and the ClearNoncleanCardWrapper closure itself does the work
// of finding contiguous dirty ranges of cards to process (and clear).
cl->do_MemRegion(mr);
}
}
}
// NOTE: For this to work correctly, it is important that
// we look for non-clean cards below (so as to catch those
// marked precleaned), rather than look explicitly for dirty
// cards (and miss those marked precleaned). In that sense,
// the name precleaned is currently somewhat of a misnomer.
void CardTableModRefBS::non_clean_card_iterate_work(MemRegion mr,
MemRegionClosure* cl) {
// The iterator itself is not MT-aware, but
// MT-aware callers and closures can use this to
// accomplish dirty card iteration in parallel. The
// iterator itself does not clear the dirty cards, or
// change their values in any manner.
void CardTableModRefBS::non_clean_card_iterate_serial(MemRegion mr,
MemRegionClosure* cl) {
for (int i = 0; i < _cur_covered_regions; i++) {
MemRegion mri = mr.intersection(_covered[i]);
if (mri.word_size() > 0) {
@ -661,7 +665,7 @@ public:
void CardTableModRefBS::verify_clean_region(MemRegion mr) {
GuaranteeNotModClosure blk(this);
non_clean_card_iterate_work(mr, &blk);
non_clean_card_iterate_serial(mr, &blk);
}
// To verify a MemRegion is entirely dirty this closure is passed to