| /* |
| * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved. |
| * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "gc/shenandoah/heuristics/shenandoahGenerationalHeuristics.hpp" |
| #include "gc/shenandoah/shenandoahCollectionSet.hpp" |
| #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" |
| #include "gc/shenandoah/shenandoahEvacInfo.hpp" |
| #include "gc/shenandoah/shenandoahGeneration.hpp" |
| #include "gc/shenandoah/shenandoahGenerationalHeap.inline.hpp" |
| #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" |
| #include "gc/shenandoah/shenandoahOldGeneration.hpp" |
| #include "gc/shenandoah/shenandoahTrace.hpp" |
| #include "logging/log.hpp" |
| |
| ShenandoahGenerationalHeuristics::ShenandoahGenerationalHeuristics(ShenandoahGeneration* generation) |
| : ShenandoahAdaptiveHeuristics(generation), _generation(generation) { |
| } |
| |
| void ShenandoahGenerationalHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) { |
| assert(collection_set->is_empty(), "Must be empty"); |
| |
| auto heap = ShenandoahGenerationalHeap::heap(); |
| size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes(); |
| |
| |
| // Check all pinned regions have updated status before choosing the collection set. |
| heap->assert_pinned_region_status(); |
| |
| // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away. |
| |
| size_t num_regions = heap->num_regions(); |
| |
| RegionData* candidates = _region_data; |
| |
| size_t cand_idx = 0; |
| size_t preselected_candidates = 0; |
| |
| size_t total_garbage = 0; |
| |
| size_t immediate_garbage = 0; |
| size_t immediate_regions = 0; |
| |
| size_t free = 0; |
| size_t free_regions = 0; |
| |
| // This counts number of humongous regions that we intend to promote in this cycle. |
| size_t humongous_regions_promoted = 0; |
| // This counts number of regular regions that will be promoted in place. |
| size_t regular_regions_promoted_in_place = 0; |
| // This counts bytes of memory used by regular regions to be promoted in place. |
| size_t regular_regions_promoted_usage = 0; |
| // This counts bytes of memory free in regular regions to be promoted in place. |
| size_t regular_regions_promoted_free = 0; |
| // This counts bytes of garbage memory in regular regions to be promoted in place. |
| size_t regular_regions_promoted_garbage = 0; |
| |
| for (size_t i = 0; i < num_regions; i++) { |
| ShenandoahHeapRegion* region = heap->get_region(i); |
| if (!_generation->contains(region)) { |
| continue; |
| } |
| size_t garbage = region->garbage(); |
| total_garbage += garbage; |
| if (region->is_empty()) { |
| free_regions++; |
| free += region_size_bytes; |
| } else if (region->is_regular()) { |
| if (!region->has_live()) { |
| // We can recycle it right away and put it in the free set. |
| immediate_regions++; |
| immediate_garbage += garbage; |
| region->make_trash_immediate(); |
| } else { |
| bool is_candidate; |
| // This is our candidate for later consideration. |
| if (collection_set->is_preselected(i)) { |
| assert(heap->is_tenurable(region), "Preselection filter"); |
| is_candidate = true; |
| preselected_candidates++; |
| // Set garbage value to maximum value to force this into the sorted collection set. |
| garbage = region_size_bytes; |
| } else if (region->is_young() && heap->is_tenurable(region)) { |
| // Note that for GLOBAL GC, region may be OLD, and OLD regions do not qualify for pre-selection |
| |
| // This region is old enough to be promoted but it was not preselected, either because its garbage is below |
| // ShenandoahOldGarbageThreshold so it will be promoted in place, or because there is not sufficient room |
| // in old gen to hold the evacuated copies of this region's live data. In both cases, we choose not to |
| // place this region into the collection set. |
| if (region->get_top_before_promote() != nullptr) { |
| // Region was included for promotion-in-place |
| regular_regions_promoted_in_place++; |
| regular_regions_promoted_usage += region->used_before_promote(); |
| regular_regions_promoted_free += region->free(); |
| regular_regions_promoted_garbage += region->garbage(); |
| } |
| is_candidate = false; |
| } else { |
| is_candidate = true; |
| } |
| if (is_candidate) { |
| candidates[cand_idx].set_region_and_garbage(region, garbage); |
| cand_idx++; |
| } |
| } |
| } else if (region->is_humongous_start()) { |
| // Reclaim humongous regions here, and count them as the immediate garbage |
| #ifdef ASSERT |
| bool reg_live = region->has_live(); |
| bool bm_live = heap->active_generation()->complete_marking_context()->is_marked(cast_to_oop(region->bottom())); |
| assert(reg_live == bm_live, |
| "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: %zu", |
| BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words()); |
| #endif |
| if (!region->has_live()) { |
| heap->trash_humongous_region_at(region); |
| |
| // Count only the start. Continuations would be counted on "trash" path |
| immediate_regions++; |
| immediate_garbage += garbage; |
| } else { |
| if (region->is_young() && heap->is_tenurable(region)) { |
| oop obj = cast_to_oop(region->bottom()); |
| size_t humongous_regions = ShenandoahHeapRegion::required_regions(obj->size() * HeapWordSize); |
| humongous_regions_promoted += humongous_regions; |
| } |
| } |
| } else if (region->is_trash()) { |
| // Count in just trashed collection set, during coalesced CM-with-UR |
| immediate_regions++; |
| immediate_garbage += garbage; |
| } |
| } |
| heap->old_generation()->set_expected_humongous_region_promotions(humongous_regions_promoted); |
| heap->old_generation()->set_expected_regular_region_promotions(regular_regions_promoted_in_place); |
| log_info(gc, ergo)("Planning to promote in place %zu humongous regions and %zu" |
| " regular regions, spanning a total of %zu used bytes", |
| humongous_regions_promoted, regular_regions_promoted_in_place, |
| humongous_regions_promoted * ShenandoahHeapRegion::region_size_bytes() + |
| regular_regions_promoted_usage); |
| |
| // Step 2. Look back at garbage statistics, and decide if we want to collect anything, |
| // given the amount of immediately reclaimable garbage. If we do, figure out the collection set. |
| |
| assert (immediate_garbage <= total_garbage, |
| "Cannot have more immediate garbage than total garbage: %zu%s vs %zu%s", |
| byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage), |
| byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage)); |
| |
| size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage); |
| |
| bool doing_promote_in_place = (humongous_regions_promoted + regular_regions_promoted_in_place > 0); |
| if (doing_promote_in_place || (preselected_candidates > 0) || (immediate_percent <= ShenandoahImmediateThreshold)) { |
| // Only young collections need to prime the collection set. |
| if (_generation->is_young()) { |
| heap->old_generation()->heuristics()->prime_collection_set(collection_set); |
| } |
| |
| // Call the subclasses to add young-gen regions into the collection set. |
| choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free); |
| } |
| |
| if (collection_set->has_old_regions()) { |
| heap->shenandoah_policy()->record_mixed_cycle(); |
| } |
| |
| size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage); |
| size_t collectable_garbage = collection_set->garbage() + immediate_garbage; |
| size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage); |
| |
| log_info(gc, ergo)("Collectable Garbage: %zu%s (%zu%%), " |
| "Immediate: %zu%s (%zu%%), %zu regions, " |
| "CSet: %zu%s (%zu%%), %zu regions", |
| |
| byte_size_in_proper_unit(collectable_garbage), |
| proper_unit_for_byte_size(collectable_garbage), |
| collectable_garbage_percent, |
| |
| byte_size_in_proper_unit(immediate_garbage), |
| proper_unit_for_byte_size(immediate_garbage), |
| immediate_percent, |
| immediate_regions, |
| |
| byte_size_in_proper_unit(collection_set->garbage()), |
| proper_unit_for_byte_size(collection_set->garbage()), |
| cset_percent, |
| collection_set->count()); |
| |
| if (collection_set->garbage() > 0) { |
| size_t young_evac_bytes = collection_set->get_young_bytes_reserved_for_evacuation(); |
| size_t promote_evac_bytes = collection_set->get_young_bytes_to_be_promoted(); |
| size_t old_evac_bytes = collection_set->get_old_bytes_reserved_for_evacuation(); |
| size_t total_evac_bytes = young_evac_bytes + promote_evac_bytes + old_evac_bytes; |
| log_info(gc, ergo)("Evacuation Targets: YOUNG: %zu%s, " |
| "PROMOTE: %zu%s, " |
| "OLD: %zu%s, " |
| "TOTAL: %zu%s", |
| byte_size_in_proper_unit(young_evac_bytes), proper_unit_for_byte_size(young_evac_bytes), |
| byte_size_in_proper_unit(promote_evac_bytes), proper_unit_for_byte_size(promote_evac_bytes), |
| byte_size_in_proper_unit(old_evac_bytes), proper_unit_for_byte_size(old_evac_bytes), |
| byte_size_in_proper_unit(total_evac_bytes), proper_unit_for_byte_size(total_evac_bytes)); |
| |
| ShenandoahEvacuationInformation evacInfo; |
| evacInfo.set_collection_set_regions(collection_set->count()); |
| evacInfo.set_collection_set_used_before(collection_set->used()); |
| evacInfo.set_collection_set_used_after(collection_set->live()); |
| evacInfo.set_collected_old(old_evac_bytes); |
| evacInfo.set_collected_promoted(promote_evac_bytes); |
| evacInfo.set_collected_young(young_evac_bytes); |
| evacInfo.set_regions_promoted_humongous(humongous_regions_promoted); |
| evacInfo.set_regions_promoted_regular(regular_regions_promoted_in_place); |
| evacInfo.set_regular_promoted_garbage(regular_regions_promoted_garbage); |
| evacInfo.set_regular_promoted_free(regular_regions_promoted_free); |
| evacInfo.set_regions_immediate(immediate_regions); |
| evacInfo.set_immediate_size(immediate_garbage); |
| evacInfo.set_free_regions(free_regions); |
| |
| ShenandoahTracer().report_evacuation_info(&evacInfo); |
| } |
| } |
| |
| |
| size_t ShenandoahGenerationalHeuristics::add_preselected_regions_to_collection_set(ShenandoahCollectionSet* cset, |
| const RegionData* data, |
| size_t size) const { |
| // cur_young_garbage represents the amount of memory to be reclaimed from young-gen. In the case that live objects |
| // are known to be promoted out of young-gen, we count this as cur_young_garbage because this memory is reclaimed |
| // from young-gen and becomes available to serve future young-gen allocation requests. |
| size_t cur_young_garbage = 0; |
| for (size_t idx = 0; idx < size; idx++) { |
| ShenandoahHeapRegion* r = data[idx].get_region(); |
| if (cset->is_preselected(r->index())) { |
| assert(ShenandoahGenerationalHeap::heap()->is_tenurable(r), "Preselected regions must have tenure age"); |
| // Entire region will be promoted, This region does not impact young-gen or old-gen evacuation reserve. |
| // This region has been pre-selected and its impact on promotion reserve is already accounted for. |
| |
| // r->used() is r->garbage() + r->get_live_data_bytes() |
| // Since all live data in this region is being evacuated from young-gen, it is as if this memory |
| // is garbage insofar as young-gen is concerned. Counting this as garbage reduces the need to |
| // reclaim highly utilized young-gen regions just for the sake of finding min_garbage to reclaim |
| // within young-gen memory. |
| |
| cur_young_garbage += r->garbage(); |
| cset->add_region(r); |
| } |
| } |
| return cur_young_garbage; |
| } |
| |
| void ShenandoahGenerationalHeuristics::log_cset_composition(ShenandoahCollectionSet* cset) const { |
| size_t collected_old = cset->get_old_bytes_reserved_for_evacuation(); |
| size_t collected_promoted = cset->get_young_bytes_to_be_promoted(); |
| size_t collected_young = cset->get_young_bytes_reserved_for_evacuation(); |
| |
| log_info(gc, ergo)( |
| "Chosen CSet evacuates young: %zu%s (of which at least: %zu%s are to be promoted), " |
| "old: %zu%s", |
| byte_size_in_proper_unit(collected_young), proper_unit_for_byte_size(collected_young), |
| byte_size_in_proper_unit(collected_promoted), proper_unit_for_byte_size(collected_promoted), |
| byte_size_in_proper_unit(collected_old), proper_unit_for_byte_size(collected_old)); |
| } |
