1/*
2 * Copyright (c) 2015, 2019, Oracle and/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
25#include "precompiled.hpp"
26#include "gc/g1/g1CollectedHeap.inline.hpp"
27#include "gc/g1/g1CollectionSet.hpp"
28#include "gc/g1/g1ConcurrentMark.inline.hpp"
29#include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
30#include "gc/g1/g1Policy.hpp"
31#include "gc/g1/g1YoungRemSetSamplingThread.hpp"
32#include "gc/g1/heapRegion.inline.hpp"
33#include "gc/g1/heapRegionRemSet.hpp"
34#include "gc/shared/suspendibleThreadSet.hpp"
35#include "memory/universe.hpp"
36#include "runtime/mutexLocker.hpp"
37
38G1YoungRemSetSamplingThread::G1YoungRemSetSamplingThread() :
39 ConcurrentGCThread(),
40 _monitor(Mutex::nonleaf,
41 "G1YoungRemSetSamplingThread monitor",
42 true,
43 Monitor::_safepoint_check_never),
44 _last_periodic_gc_attempt_s(os::elapsedTime()),
45 _vtime_accum(0) {
46 set_name("G1 Young RemSet Sampling");
47 create_and_start();
48}
49
50void G1YoungRemSetSamplingThread::sleep_before_next_cycle() {
51 MonitorLocker ml(&_monitor, Mutex::_no_safepoint_check_flag);
52 if (!should_terminate()) {
53 uintx waitms = G1ConcRefinementServiceIntervalMillis;
54 ml.wait(waitms);
55 }
56}
57
58bool G1YoungRemSetSamplingThread::should_start_periodic_gc() {
59 // If we are currently in a concurrent mark we are going to uncommit memory soon.
60 if (G1CollectedHeap::heap()->concurrent_mark()->cm_thread()->during_cycle()) {
61 log_debug(gc, periodic)("Concurrent cycle in progress. Skipping.");
62 return false;
63 }
64
65 // Check if enough time has passed since the last GC.
66 uintx time_since_last_gc = (uintx)Universe::heap()->millis_since_last_gc();
67 if ((time_since_last_gc < G1PeriodicGCInterval)) {
68 log_debug(gc, periodic)("Last GC occurred " UINTX_FORMAT "ms before which is below threshold " UINTX_FORMAT "ms. Skipping.",
69 time_since_last_gc, G1PeriodicGCInterval);
70 return false;
71 }
72
73 // Check if load is lower than max.
74 double recent_load;
75 if ((G1PeriodicGCSystemLoadThreshold > 0.0f) &&
76 (os::loadavg(&recent_load, 1) == -1 || recent_load > G1PeriodicGCSystemLoadThreshold)) {
77 log_debug(gc, periodic)("Load %1.2f is higher than threshold %1.2f. Skipping.",
78 recent_load, G1PeriodicGCSystemLoadThreshold);
79 return false;
80 }
81
82 return true;
83}
84
85void G1YoungRemSetSamplingThread::check_for_periodic_gc(){
86 // If disabled, just return.
87 if (G1PeriodicGCInterval == 0) {
88 return;
89 }
90 if ((os::elapsedTime() - _last_periodic_gc_attempt_s) > (G1PeriodicGCInterval / 1000.0)) {
91 log_debug(gc, periodic)("Checking for periodic GC.");
92 if (should_start_periodic_gc()) {
93 if (!G1CollectedHeap::heap()->try_collect(GCCause::_g1_periodic_collection,
94 false /* retry_on_vmop_failure */)) {
95 log_debug(gc, periodic)("GC request denied. Skipping.");
96 }
97 }
98 _last_periodic_gc_attempt_s = os::elapsedTime();
99 }
100}
101
102void G1YoungRemSetSamplingThread::run_service() {
103 double vtime_start = os::elapsedVTime();
104
105 // Print a message about periodic GC configuration.
106 if (G1PeriodicGCInterval != 0) {
107 log_info(gc)("Periodic GC enabled with interval " UINTX_FORMAT "ms", G1PeriodicGCInterval);
108 } else {
109 log_info(gc)("Periodic GC disabled");
110 }
111
112 while (!should_terminate()) {
113 sample_young_list_rs_lengths();
114
115 if (os::supports_vtime()) {
116 _vtime_accum = (os::elapsedVTime() - vtime_start);
117 } else {
118 _vtime_accum = 0.0;
119 }
120
121 check_for_periodic_gc();
122
123 sleep_before_next_cycle();
124 }
125}
126
127void G1YoungRemSetSamplingThread::stop_service() {
128 MutexLocker x(&_monitor, Mutex::_no_safepoint_check_flag);
129 _monitor.notify();
130}
131
132class G1YoungRemSetSamplingClosure : public HeapRegionClosure {
133 SuspendibleThreadSetJoiner* _sts;
134 size_t _regions_visited;
135 size_t _sampled_rs_lengths;
136public:
137 G1YoungRemSetSamplingClosure(SuspendibleThreadSetJoiner* sts) :
138 HeapRegionClosure(), _sts(sts), _regions_visited(0), _sampled_rs_lengths(0) { }
139
140 virtual bool do_heap_region(HeapRegion* r) {
141 size_t rs_length = r->rem_set()->occupied();
142 _sampled_rs_lengths += rs_length;
143
144 // Update the collection set policy information for this region
145 G1CollectedHeap::heap()->collection_set()->update_young_region_prediction(r, rs_length);
146
147 _regions_visited++;
148
149 if (_regions_visited == 10) {
150 if (_sts->should_yield()) {
151 _sts->yield();
152 // A gc may have occurred and our sampling data is stale and further
153 // traversal of the collection set is unsafe
154 return true;
155 }
156 _regions_visited = 0;
157 }
158 return false;
159 }
160
161 size_t sampled_rs_lengths() const { return _sampled_rs_lengths; }
162};
163
164void G1YoungRemSetSamplingThread::sample_young_list_rs_lengths() {
165 SuspendibleThreadSetJoiner sts;
166 G1CollectedHeap* g1h = G1CollectedHeap::heap();
167 G1Policy* policy = g1h->policy();
168
169 if (policy->use_adaptive_young_list_length()) {
170 G1YoungRemSetSamplingClosure cl(&sts);
171
172 G1CollectionSet* g1cs = g1h->collection_set();
173 g1cs->iterate(&cl);
174
175 if (cl.is_complete()) {
176 policy->revise_young_list_target_length_if_necessary(cl.sampled_rs_lengths());
177 }
178 }
179}
180