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src/share/vm/gc_implementation/g1/g1ParScanThreadState.cpp
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rev 7471 : 8060025: Object copy time regressions after JDK-8031323 and JDK-8057536
Summary: Evaluate and improve object copy time by micro-optimizations and splitting out slow and fast paths aggressively.
Reviewed-by:
Contributed-by: Tony Printezis <tprintezis@twitter.com>, Thomas Schatzl <thomas.schatzl@oracle.com>
rev 7473 : imported patch mikael-refactor-cset-state
@@ -36,10 +36,11 @@
_dcq(&g1h->dirty_card_queue_set()),
_ct_bs(g1h->g1_barrier_set()),
_g1_rem(g1h->g1_rem_set()),
_hash_seed(17), _queue_num(queue_num),
_term_attempts(0),
+ _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
_age_table(false), _scanner(g1h, rp),
_strong_roots_time(0), _term_time(0) {
_scanner.set_par_scan_thread_state(this);
// we allocate G1YoungSurvRateNumRegions plus one entries, since
// we "sacrifice" entry 0 to keep track of surviving bytes for
@@ -57,10 +58,16 @@
_surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
_g1_par_allocator = G1ParGCAllocator::create_allocator(_g1h);
+ _dest[InCSetState::NotInCSet] = InCSetState::NotInCSet;
+ // The dest for Young is used when the objects are aged enough to
+ // need to be moved to the next space.
+ _dest[InCSetState::Young] = InCSetState::Old;
+ _dest[InCSetState::Old] = InCSetState::Old;
+
_start = os::elapsedTime();
}
G1ParScanThreadState::~G1ParScanThreadState() {
_g1_par_allocator->retire_alloc_buffers();
@@ -148,56 +155,98 @@
dispatch_reference(ref);
}
} while (!_refs->is_empty());
}
-oop G1ParScanThreadState::copy_to_survivor_space(oop const old,
+HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
+ InCSetState* dest,
+ size_t word_sz,
+ AllocationContext_t const context) {
+ assert(state.is_in_cset_or_humongous(), err_msg("Unexpected state: %u", state.value()));
+ assert(dest->is_in_cset_or_humongous(), err_msg("Unexpected dest: %u", dest->value()));
+
+ // Right now we only have two types of regions (young / old) so
+ // let's keep the logic here simple. We can generalize it when necessary.
+ if (dest->is_young()) {
+ HeapWord* const obj_ptr = _g1_par_allocator->allocate(InCSetState::Old,
+ word_sz, context);
+ if (obj_ptr == NULL) {
+ return NULL;
+ }
+ // Make sure that we won't attempt to copy any other objects out
+ // of a survivor region (given that apparently we cannot allocate
+ // any new ones) to avoid coming into this slow path.
+ _tenuring_threshold = 0;
+ dest->set_old();
+ return obj_ptr;
+ } else {
+ assert(dest->is_old(), err_msg("Unexpected dest: %u", dest->value()));
+ // no other space to try.
+ return NULL;
+ }
+}
+
+InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
+ if (state.is_young()) {
+ age = !m->has_displaced_mark_helper() ? m->age()
+ : m->displaced_mark_helper()->age();
+ if (age < _tenuring_threshold) {
+ return state;
+ }
+ }
+ return dest(state);
+}
+
+oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
+ oop const old,
markOop const old_mark) {
- size_t word_sz = old->size();
- HeapRegion* from_region = _g1h->heap_region_containing_raw(old);
+ const size_t word_sz = old->size();
+ HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
// +1 to make the -1 indexes valid...
- int young_index = from_region->young_index_in_cset()+1;
+ const int young_index = from_region->young_index_in_cset()+1;
assert( (from_region->is_young() && young_index > 0) ||
(!from_region->is_young() && young_index == 0), "invariant" );
- G1CollectorPolicy* g1p = _g1h->g1_policy();
- uint age = old_mark->has_displaced_mark_helper() ? old_mark->displaced_mark_helper()->age()
- : old_mark->age();
- GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
- word_sz);
- AllocationContext_t context = from_region->allocation_context();
- HeapWord* obj_ptr = _g1_par_allocator->allocate(alloc_purpose, word_sz, context);
-#ifndef PRODUCT
- // Should this evacuation fail?
- if (_g1h->evacuation_should_fail()) {
- if (obj_ptr != NULL) {
- _g1_par_allocator->undo_allocation(alloc_purpose, obj_ptr, word_sz, context);
- obj_ptr = NULL;
- }
- }
-#endif // !PRODUCT
+ const AllocationContext_t context = from_region->allocation_context();
+
+ uint age = 0;
+ InCSetState dest_state = next_state(state, old_mark, age);
+ HeapWord* obj_ptr = _g1_par_allocator->plab_allocate(dest_state, word_sz, context);
+ // PLAB allocations should succeed most of the time, so we'll
+ // normally check against NULL once and that's it.
+ if (obj_ptr == NULL) {
+ obj_ptr = _g1_par_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context);
+ if (obj_ptr == NULL) {
+ obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context);
if (obj_ptr == NULL) {
// This will either forward-to-self, or detect that someone else has
// installed a forwarding pointer.
return _g1h->handle_evacuation_failure_par(this, old);
}
+ }
+ }
- oop obj = oop(obj_ptr);
+ assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
+#ifndef PRODUCT
+ // Should this evacuation fail?
+ if (_g1h->evacuation_should_fail()) {
+ // Doing this after all the allocation attempts also tests the
+ // undo_allocation() method too.
+ _g1_par_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
+ return _g1h->handle_evacuation_failure_par(this, old);
+ }
+#endif // !PRODUCT
// We're going to allocate linearly, so might as well prefetch ahead.
Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
- oop forward_ptr = old->forward_to_atomic(obj);
+ const oop obj = oop(obj_ptr);
+ const oop forward_ptr = old->forward_to_atomic(obj);
if (forward_ptr == NULL) {
Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
- // alloc_purpose is just a hint to allocate() above, recheck the type of region
- // we actually allocated from and update alloc_purpose accordingly
- HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr);
- alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured;
-
- if (g1p->track_object_age(alloc_purpose)) {
+ if (dest_state.is_young()) {
if (age < markOopDesc::max_age) {
age++;
}
if (old_mark->has_displaced_mark_helper()) {
// In this case, we have to install the mark word first,
@@ -213,33 +262,38 @@
} else {
obj->set_mark(old_mark);
}
if (G1StringDedup::is_enabled()) {
- G1StringDedup::enqueue_from_evacuation(from_region->is_young(),
- to_region->is_young(),
+ const bool is_from_young = state.is_young();
+ const bool is_to_young = dest_state.is_young();
+ assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
+ "sanity");
+ assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
+ "sanity");
+ G1StringDedup::enqueue_from_evacuation(is_from_young,
+ is_to_young,
queue_num(),
obj);
}
- size_t* surv_young_words = surviving_young_words();
+ size_t* const surv_young_words = surviving_young_words();
surv_young_words[young_index] += word_sz;
if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
// We keep track of the next start index in the length field of
// the to-space object. The actual length can be found in the
// length field of the from-space object.
arrayOop(obj)->set_length(0);
oop* old_p = set_partial_array_mask(old);
push_on_queue(old_p);
} else {
- // No point in using the slower heap_region_containing() method,
- // given that we know obj is in the heap.
- _scanner.set_region(_g1h->heap_region_containing_raw(obj));
+ HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
+ _scanner.set_region(to_region);
obj->oop_iterate_backwards(&_scanner);
}
+ return obj;
} else {
- _g1_par_allocator->undo_allocation(alloc_purpose, obj_ptr, word_sz, context);
- obj = forward_ptr;
+ _g1_par_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
+ return forward_ptr;
}
- return obj;
}
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