1 /*
2 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24 #include "precompiled.hpp"
25
26 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
27 #include "gc/shenandoah/mode/shenandoahMode.hpp"
28 #include "gc/shenandoah/shenandoahControlThread.hpp"
29 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
30 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
31 #include "gc/shenandoah/shenandoahRegulatorThread.hpp"
32 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
33 #include "logging/log.hpp"
34
35 static ShenandoahHeuristics* get_heuristics(ShenandoahGeneration* nullable) {
36 return nullable != nullptr ? nullable->heuristics() : nullptr;
37 }
38
39 ShenandoahRegulatorThread::ShenandoahRegulatorThread(ShenandoahControlThread* control_thread) :
40 ConcurrentGCThread(),
41 _control_thread(control_thread),
42 _sleep(ShenandoahControlIntervalMin),
43 _last_sleep_adjust_time(os::elapsedTime()) {
44
45 ShenandoahHeap* heap = ShenandoahHeap::heap();
46 _old_heuristics = get_heuristics(heap->old_generation());
47 _young_heuristics = get_heuristics(heap->young_generation());
48 _global_heuristics = get_heuristics(heap->global_generation());
49
50 create_and_start();
51 }
52
53 void ShenandoahRegulatorThread::run_service() {
54 if (ShenandoahHeap::heap()->mode()->is_generational()) {
55 if (ShenandoahAllowOldMarkingPreemption) {
56 regulate_concurrent_cycles();
57 } else {
58 regulate_interleaved_cycles();
59 }
60 } else {
61 regulate_heap();
62 }
63
64 log_info(gc)("%s: Done.", name());
65 }
66
67 void ShenandoahRegulatorThread::regulate_concurrent_cycles() {
68 assert(_young_heuristics != nullptr, "Need young heuristics.");
69 assert(_old_heuristics != nullptr, "Need old heuristics.");
70
71 while (!should_terminate()) {
72 ShenandoahControlThread::GCMode mode = _control_thread->gc_mode();
73 if (mode == ShenandoahControlThread::none) {
74 if (should_unload_classes()) {
75 if (request_concurrent_gc(ShenandoahControlThread::select_global_generation())) {
76 log_info(gc)("Heuristics request for global (unload classes) accepted.");
77 }
78 } else {
79 if (_young_heuristics->should_start_gc()) {
80 if (start_old_cycle()) {
81 log_info(gc)("Heuristics request for old collection accepted");
82 } else if (request_concurrent_gc(YOUNG)) {
83 log_info(gc)("Heuristics request for young collection accepted");
84 }
85 }
86 }
87 } else if (mode == ShenandoahControlThread::servicing_old) {
88 if (start_young_cycle()) {
89 log_info(gc)("Heuristics request to interrupt old for young collection accepted");
90 }
91 }
92
93 regulator_sleep();
94 }
95 }
96
97 void ShenandoahRegulatorThread::regulate_interleaved_cycles() {
98 assert(_young_heuristics != nullptr, "Need young heuristics.");
99 assert(_global_heuristics != nullptr, "Need global heuristics.");
100
101 while (!should_terminate()) {
102 if (_control_thread->gc_mode() == ShenandoahControlThread::none) {
103 if (start_global_cycle()) {
104 log_info(gc)("Heuristics request for global collection accepted.");
105 } else if (start_young_cycle()) {
106 log_info(gc)("Heuristics request for young collection accepted.");
107 }
108 }
109
110 regulator_sleep();
111 }
112 }
113
114 void ShenandoahRegulatorThread::regulate_heap() {
115 assert(_global_heuristics != nullptr, "Need global heuristics.");
116
117 while (!should_terminate()) {
118 if (_control_thread->gc_mode() == ShenandoahControlThread::none) {
119 if (start_global_cycle()) {
120 log_info(gc)("Heuristics request for global collection accepted.");
121 }
122 }
123
124 regulator_sleep();
125 }
126 }
127
128 void ShenandoahRegulatorThread::regulator_sleep() {
129 // Wait before performing the next action. If allocation happened during this wait,
130 // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle,
131 // back off exponentially.
132 double current = os::elapsedTime();
133
134 if (_heap_changed.try_unset()) {
135 _sleep = ShenandoahControlIntervalMin;
136 } else if ((current - _last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){
137 _sleep = MIN2<int>(ShenandoahControlIntervalMax, MAX2(1, _sleep * 2));
138 _last_sleep_adjust_time = current;
139 }
140
141 os::naked_short_sleep(_sleep);
142 if (LogTarget(Debug, gc, thread)::is_enabled()) {
143 double elapsed = os::elapsedTime() - current;
144 double hiccup = elapsed - double(_sleep);
145 if (hiccup > 0.001) {
146 log_debug(gc, thread)("Regulator hiccup time: %.3fs", hiccup);
147 }
148 }
149 }
150
151 bool ShenandoahRegulatorThread::start_old_cycle() {
152 // TODO: These first two checks might be vestigial
153 return !ShenandoahHeap::heap()->doing_mixed_evacuations()
154 && !ShenandoahHeap::heap()->collection_set()->has_old_regions()
155 && _old_heuristics->should_start_gc()
156 && request_concurrent_gc(OLD);
157 }
158
159 bool ShenandoahRegulatorThread::request_concurrent_gc(ShenandoahGenerationType generation) {
160 double now = os::elapsedTime();
161 bool accepted = _control_thread->request_concurrent_gc(generation);
162 if (LogTarget(Debug, gc, thread)::is_enabled() && accepted) {
163 double wait_time = os::elapsedTime() - now;
164 if (wait_time > 0.001) {
165 log_debug(gc, thread)("Regulator waited %.3fs for control thread to acknowledge request.", wait_time);
166 }
167 }
168 return accepted;
169 }
170
171 bool ShenandoahRegulatorThread::start_young_cycle() {
172 return _young_heuristics->should_start_gc() && request_concurrent_gc(YOUNG);
173 }
174
175 bool ShenandoahRegulatorThread::start_global_cycle() {
176 return _global_heuristics->should_start_gc() && request_concurrent_gc(ShenandoahControlThread::select_global_generation());
177 }
178
179 void ShenandoahRegulatorThread::stop_service() {
180 log_info(gc)("%s: Stop requested.", name());
181 }
182
183 bool ShenandoahRegulatorThread::should_unload_classes() {
184 // The heuristics delegate this decision to the collector policy, which is based on the number
185 // of cycles started.
186 return _global_heuristics->should_unload_classes();
187 }
188