179 lines
8.2 KiB
C++
179 lines
8.2 KiB
C++
/*
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* Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "gc/g1/g1CollectionSetChooser.hpp"
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#include "gc/g1/g1RemSetTrackingPolicy.hpp"
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#include "gc/g1/heapRegion.inline.hpp"
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#include "gc/g1/heapRegionRemSet.hpp"
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#include "runtime/safepoint.hpp"
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bool G1RemSetTrackingPolicy::needs_scan_for_rebuild(HeapRegion* r) const {
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// All non-free, non-young, non-closed archive regions need to be scanned for references;
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// At every gc we gather references to other regions in young, and closed archive
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// regions by definition do not have references going outside the closed archive.
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// Free regions trivially do not need scanning because they do not contain live
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// objects.
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return !(r->is_young() || r->is_closed_archive() || r->is_free());
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}
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void G1RemSetTrackingPolicy::update_at_allocate(HeapRegion* r) {
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if (r->is_young()) {
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// Always collect remembered set for young regions.
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r->rem_set()->set_state_complete();
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} else if (r->is_humongous()) {
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// Collect remembered sets for humongous regions by default to allow eager reclaim.
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r->rem_set()->set_state_complete();
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} else if (r->is_archive()) {
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// Archive regions never move ever. So never build remembered sets for them.
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r->rem_set()->set_state_empty();
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} else if (r->is_old()) {
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// By default, do not create remembered set for new old regions.
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r->rem_set()->set_state_empty();
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} else {
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guarantee(false, "Unhandled region %u with heap region type %s", r->hrm_index(), r->get_type_str());
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}
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}
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void G1RemSetTrackingPolicy::update_at_free(HeapRegion* r) {
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/* nothing to do */
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}
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static void print_before_rebuild(HeapRegion* r, bool selected_for_rebuild, size_t total_live_bytes, size_t live_bytes) {
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log_trace(gc, remset, tracking)("Before rebuild region %u "
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"(ntams: " PTR_FORMAT ") "
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"total_live_bytes " SIZE_FORMAT " "
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"selected %s "
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"(live_bytes " SIZE_FORMAT " "
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"next_marked " SIZE_FORMAT " "
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"marked " SIZE_FORMAT " "
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"type %s)",
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r->hrm_index(),
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p2i(r->next_top_at_mark_start()),
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total_live_bytes,
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BOOL_TO_STR(selected_for_rebuild),
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live_bytes,
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r->next_marked_bytes(),
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r->marked_bytes(),
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r->get_type_str());
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}
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bool G1RemSetTrackingPolicy::update_humongous_before_rebuild(HeapRegion* r, bool is_live) {
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assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
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assert(r->is_humongous(), "Region %u should be humongous", r->hrm_index());
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if (r->is_archive()) {
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return false;
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}
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assert(!r->rem_set()->is_updating(), "Remembered set of region %u is updating before rebuild", r->hrm_index());
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bool selected_for_rebuild = false;
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// For humongous regions, to be of interest for rebuilding the remembered set the following must apply:
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// - We always try to update the remembered sets of humongous regions containing
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// type arrays as they might have been reset after full gc.
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if (is_live && oop(r->humongous_start_region()->bottom())->is_typeArray() && !r->rem_set()->is_tracked()) {
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r->rem_set()->set_state_updating();
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selected_for_rebuild = true;
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}
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size_t const live_bytes = is_live ? HeapRegion::GrainBytes : 0;
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print_before_rebuild(r, selected_for_rebuild, live_bytes, live_bytes);
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return selected_for_rebuild;
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}
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bool G1RemSetTrackingPolicy::update_before_rebuild(HeapRegion* r, size_t live_bytes) {
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assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
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assert(!r->is_humongous(), "Region %u is humongous", r->hrm_index());
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// Only consider updating the remembered set for old gen regions - excluding archive regions
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// which never move (but are "Old" regions).
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if (!r->is_old() || r->is_archive()) {
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return false;
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}
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assert(!r->rem_set()->is_updating(), "Remembered set of region %u is updating before rebuild", r->hrm_index());
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size_t between_ntams_and_top = (r->top() - r->next_top_at_mark_start()) * HeapWordSize;
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size_t total_live_bytes = live_bytes + between_ntams_and_top;
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bool selected_for_rebuild = false;
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// For old regions, to be of interest for rebuilding the remembered set the following must apply:
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// - They must contain some live data in them.
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// - Only need to rebuild non-complete remembered sets.
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// - Otherwise only add those old gen regions which occupancy is low enough that there
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// is a chance that we will ever evacuate them in the mixed gcs.
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if ((total_live_bytes > 0) &&
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G1CollectionSetChooser::region_occupancy_low_enough_for_evac(total_live_bytes) &&
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!r->rem_set()->is_tracked()) {
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r->rem_set()->set_state_updating();
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selected_for_rebuild = true;
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}
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print_before_rebuild(r, selected_for_rebuild, total_live_bytes, live_bytes);
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return selected_for_rebuild;
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}
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void G1RemSetTrackingPolicy::update_after_rebuild(HeapRegion* r) {
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assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
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if (r->is_old_or_humongous_or_archive()) {
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if (r->rem_set()->is_updating()) {
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assert(!r->is_archive(), "Archive region %u with remembered set", r->hrm_index());
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r->rem_set()->set_state_complete();
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}
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G1CollectedHeap* g1h = G1CollectedHeap::heap();
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// We can drop remembered sets of humongous regions that have a too large remembered set:
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// We will never try to eagerly reclaim or move them anyway until the next concurrent
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// cycle as e.g. remembered set entries will always be added.
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if (r->is_starts_humongous() && !g1h->is_potential_eager_reclaim_candidate(r)) {
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// Handle HC regions with the HS region.
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uint const size_in_regions = (uint)g1h->humongous_obj_size_in_regions(oop(r->bottom())->size());
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uint const region_idx = r->hrm_index();
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for (uint j = region_idx; j < (region_idx + size_in_regions); j++) {
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HeapRegion* const cur = g1h->region_at(j);
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assert(!cur->is_continues_humongous() || cur->rem_set()->is_empty(),
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"Continues humongous region %u remset should be empty", j);
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cur->rem_set()->clear_locked(true /* only_cardset */);
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}
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}
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G1ConcurrentMark* cm = G1CollectedHeap::heap()->concurrent_mark();
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log_trace(gc, remset, tracking)("After rebuild region %u "
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"(ntams " PTR_FORMAT " "
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"liveness " SIZE_FORMAT " "
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"next_marked_bytes " SIZE_FORMAT " "
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"remset occ " SIZE_FORMAT " "
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"size " SIZE_FORMAT ")",
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r->hrm_index(),
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p2i(r->next_top_at_mark_start()),
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cm->liveness(r->hrm_index()) * HeapWordSize,
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r->next_marked_bytes(),
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r->rem_set()->occupied_locked(),
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r->rem_set()->mem_size());
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}
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}
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