1 /*
2 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
3 * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "gc/shenandoah/heuristics/shenandoahGlobalHeuristics.hpp"
27 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
28 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
29 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
30 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
31 #include "utilities/quickSort.hpp"
32
33 ShenandoahGlobalHeuristics::ShenandoahGlobalHeuristics(ShenandoahGlobalGeneration* generation)
34 : ShenandoahGenerationalHeuristics(generation) {
35 }
36
37
38 void ShenandoahGlobalHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
39 RegionData* data, size_t size,
40 size_t actual_free) {
41 // Better select garbage-first regions
42 QuickSort::sort<RegionData>(data, (int) size, compare_by_garbage);
43
44 choose_global_collection_set(cset, data, size, actual_free, 0 /* cur_young_garbage */);
45
46 log_cset_composition(cset);
47 }
48
49
50 void ShenandoahGlobalHeuristics::choose_global_collection_set(ShenandoahCollectionSet* cset,
51 const ShenandoahHeuristics::RegionData* data,
52 size_t size, size_t actual_free,
53 size_t cur_young_garbage) const {
54 auto heap = ShenandoahGenerationalHeap::heap();
55 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
56 size_t capacity = heap->young_generation()->max_capacity();
57 size_t garbage_threshold = region_size_bytes * ShenandoahGarbageThreshold / 100;
58 size_t ignore_threshold = region_size_bytes * ShenandoahIgnoreGarbageThreshold / 100;
59 const uint tenuring_threshold = heap->age_census()->tenuring_threshold();
60
61 size_t young_evac_reserve = heap->young_generation()->get_evacuation_reserve();
62 size_t old_evac_reserve = heap->old_generation()->get_evacuation_reserve();
63 size_t max_young_cset = (size_t) (young_evac_reserve / ShenandoahEvacWaste);
64 size_t young_cur_cset = 0;
65 size_t max_old_cset = (size_t) (old_evac_reserve / ShenandoahOldEvacWaste);
66 size_t old_cur_cset = 0;
67
68 // Figure out how many unaffiliated young regions are dedicated to mutator and to evacuator. Allow the young
69 // collector's unaffiliated regions to be transferred to old-gen if old-gen has more easily reclaimed garbage
70 // than young-gen. At the end of this cycle, any excess regions remaining in old-gen will be transferred back
71 // to young. Do not transfer the mutator's unaffiliated regions to old-gen. Those must remain available
72 // to the mutator as it needs to be able to consume this memory during concurrent GC.
73
74 size_t unaffiliated_young_regions = heap->young_generation()->free_unaffiliated_regions();
75 size_t unaffiliated_young_memory = unaffiliated_young_regions * region_size_bytes;
76
77 if (unaffiliated_young_memory > max_young_cset) {
78 size_t unaffiliated_mutator_memory = unaffiliated_young_memory - max_young_cset;
79 unaffiliated_young_memory -= unaffiliated_mutator_memory;
80 unaffiliated_young_regions = unaffiliated_young_memory / region_size_bytes; // round down
81 unaffiliated_young_memory = unaffiliated_young_regions * region_size_bytes;
82 }
83
84 // We'll affiliate these unaffiliated regions with either old or young, depending on need.
85 max_young_cset -= unaffiliated_young_memory;
86
87 // Keep track of how many regions we plan to transfer from young to old.
88 size_t regions_transferred_to_old = 0;
89
90 size_t free_target = (capacity * ShenandoahMinFreeThreshold) / 100 + max_young_cset;
91 size_t min_garbage = (free_target > actual_free) ? (free_target - actual_free) : 0;
92
93 log_info(gc, ergo)("Adaptive CSet Selection for GLOBAL. Max Young Evacuation: %zu"
94 "%s, Max Old Evacuation: %zu%s, Actual Free: %zu%s.",
95 byte_size_in_proper_unit(max_young_cset), proper_unit_for_byte_size(max_young_cset),
96 byte_size_in_proper_unit(max_old_cset), proper_unit_for_byte_size(max_old_cset),
97 byte_size_in_proper_unit(actual_free), proper_unit_for_byte_size(actual_free));
98
99 for (size_t idx = 0; idx < size; idx++) {
100 ShenandoahHeapRegion* r = data[idx].get_region();
101 assert(!cset->is_preselected(r->index()), "There should be no preselected regions during GLOBAL GC");
102 bool add_region = false;
103 if (r->is_old() || (r->age() >= tenuring_threshold)) {
104 size_t new_cset = old_cur_cset + r->get_live_data_bytes();
105 if ((r->garbage() > garbage_threshold)) {
106 while ((new_cset > max_old_cset) && (unaffiliated_young_regions > 0)) {
107 unaffiliated_young_regions--;
108 regions_transferred_to_old++;
109 max_old_cset += region_size_bytes / ShenandoahOldEvacWaste;
110 }
111 }
112 if ((new_cset <= max_old_cset) && (r->garbage() > garbage_threshold)) {
113 add_region = true;
114 old_cur_cset = new_cset;
115 }
116 } else {
117 assert(r->is_young() && (r->age() < tenuring_threshold), "DeMorgan's law (assuming r->is_affiliated)");
118 size_t new_cset = young_cur_cset + r->get_live_data_bytes();
119 size_t region_garbage = r->garbage();
120 size_t new_garbage = cur_young_garbage + region_garbage;
121 bool add_regardless = (region_garbage > ignore_threshold) && (new_garbage < min_garbage);
122
123 if (add_regardless || (r->garbage() > garbage_threshold)) {
124 while ((new_cset > max_young_cset) && (unaffiliated_young_regions > 0)) {
125 unaffiliated_young_regions--;
126 max_young_cset += region_size_bytes / ShenandoahEvacWaste;
127 }
128 }
129 if ((new_cset <= max_young_cset) && (add_regardless || (region_garbage > garbage_threshold))) {
130 add_region = true;
131 young_cur_cset = new_cset;
132 cur_young_garbage = new_garbage;
133 }
134 }
135 if (add_region) {
136 cset->add_region(r);
137 }
138 }
139
140 if (regions_transferred_to_old > 0) {
141 heap->generation_sizer()->force_transfer_to_old(regions_transferred_to_old);
142 heap->young_generation()->set_evacuation_reserve(young_evac_reserve - regions_transferred_to_old * region_size_bytes);
143 heap->old_generation()->set_evacuation_reserve(old_evac_reserve + regions_transferred_to_old * region_size_bytes);
144 }
145 }