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8179679: Rearrange filters before card scanning

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Implement micro-optimizations in the card scanning code enabled by JDK-8177044.

Reviewed-by: sjohanss, ehelin
This commit is contained in:
Thomas Schatzl 2017-07-06 12:11:20 +02:00
parent 10afb6f4f0
commit 3df0f64e1f
2 changed files with 37 additions and 23 deletions
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57
hotspot/src/share/vm/gc/g1/g1RemSet.cpp
View file

@ -344,19 +344,11 @@ G1ScanRSForRegionClosure::G1ScanRSForRegionClosure(G1RemSetScanState* scan_state
_ct_bs = _g1h->g1_barrier_set();
}
void G1ScanRSForRegionClosure::scan_card(size_t index, HeapWord* card_start, HeapRegion *r) {
MemRegion card_region(card_start, BOTConstants::N_words);
MemRegion pre_gc_allocated(r->bottom(), _scan_state->scan_top(r->hrm_index()));
MemRegion mr = pre_gc_allocated.intersection(card_region);
if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
// We make the card as "claimed" lazily (so races are possible
// but they're benign), which reduces the number of duplicate
// scans (the rsets of the regions in the cset can intersect).
_ct_bs->set_card_claimed(index);
_scan_objs_on_card_cl->set_region(r);
r->oops_on_card_seq_iterate_careful<true>(mr, _scan_objs_on_card_cl);
_cards_scanned++;
}
void G1ScanRSForRegionClosure::scan_card(MemRegion mr, uint region_idx_for_card) {
HeapRegion* const card_region = _g1h->region_at(region_idx_for_card);
_scan_objs_on_card_cl->set_region(card_region);
card_region->oops_on_card_seq_iterate_careful<true>(mr, _scan_objs_on_card_cl);
_cards_scanned++;
}
void G1ScanRSForRegionClosure::scan_strong_code_roots(HeapRegion* r) {
@ -365,6 +357,11 @@ void G1ScanRSForRegionClosure::scan_strong_code_roots(HeapRegion* r) {
_strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
}
void G1ScanRSForRegionClosure::claim_card(size_t card_index, const uint region_idx_for_card){
_ct_bs->set_card_claimed(card_index);
_scan_state->add_dirty_region(region_idx_for_card);
}
bool G1ScanRSForRegionClosure::doHeapRegion(HeapRegion* r) {
assert(r->in_collection_set(), "should only be called on elements of CS.");
uint region_idx = r->hrm_index();
@ -394,18 +391,34 @@ bool G1ScanRSForRegionClosure::doHeapRegion(HeapRegion* r) {
_cards_skipped++;
continue;
}
HeapWord* card_start = _g1h->bot()->address_for_index(card_index);
HeapRegion* card_region = _g1h->heap_region_containing(card_start);
_cards_claimed++;
_scan_state->add_dirty_region(card_region->hrm_index());
// If the card is dirty, then we will scan it during updateRS.
if (!card_region->in_collection_set() &&
!_ct_bs->is_card_dirty(card_index)) {
scan_card(card_index, card_start, card_region);
// If the card is dirty, then G1 will scan it during Update RS.
if (_ct_bs->is_card_claimed(card_index) || _ct_bs->is_card_dirty(card_index)) {
continue;
}
HeapWord* const card_start = _g1h->bot()->address_for_index(card_index);
uint const region_idx_for_card = _g1h->addr_to_region(card_start);
assert(_g1h->region_at(region_idx_for_card)->is_in_reserved(card_start),
"Card start " PTR_FORMAT " to scan outside of region %u", p2i(card_start), _g1h->region_at(region_idx_for_card)->hrm_index());
HeapWord* const top = _scan_state->scan_top(region_idx_for_card);
if (card_start >= top) {
continue;
}
// We claim lazily (so races are possible but they're benign), which reduces the
// number of duplicate scans (the rsets of the regions in the cset can intersect).
// Claim the card after checking bounds above: the remembered set may contain
// random cards into current survivor, and we would then have an incorrectly
// claimed card in survivor space. Card table clear does not reset the card table
// of survivor space regions.
claim_card(card_index, region_idx_for_card);
MemRegion const mr(card_start, MIN2(card_start + BOTConstants::N_words, top));
scan_card(mr, region_idx_for_card);
}
if (_scan_state->set_iter_complete(region_idx)) {
// Scan the strong code root list attached to the current region

3
hotspot/src/share/vm/gc/g1/g1RemSet.hpp
View file

@ -179,7 +179,8 @@ class G1ScanRSForRegionClosure : public HeapRegionClosure {
double _strong_code_root_scan_time_sec;
uint _worker_i;
void scan_card(size_t index, HeapWord* card_start, HeapRegion *r);
void claim_card(size_t card_index, const uint region_idx_for_card);
void scan_card(MemRegion mr, uint region_idx_for_card);
void scan_strong_code_roots(HeapRegion* r);
public:
G1ScanRSForRegionClosure(G1RemSetScanState* scan_state,