1 /*
2 * Copyright (c) 2015, 2017, 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 "runtime/mutexLocker.hpp"
36
37 G1YoungRemSetSamplingThread::G1YoungRemSetSamplingThread() :
38 ConcurrentGCThread(),
39 _monitor(Mutex::nonleaf,
40 "G1YoungRemSetSamplingThread monitor",
41 true,
42 Monitor::_safepoint_check_never),
43 _last_periodic_gc_attempt_s(os::elapsedTime()) {
44 set_name("G1 Young RemSet Sampling");
45 create_and_start();
46 }
47
48 void G1YoungRemSetSamplingThread::sleep_before_next_cycle() {
49 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
50 if (!should_terminate()) {
51 uintx waitms = G1ConcRefinementServiceIntervalMillis;
52 _monitor.wait(Mutex::_no_safepoint_check_flag, waitms);
53 }
54 }
55
56 bool G1YoungRemSetSamplingThread::should_start_periodic_gc() {
57 // If we are currently in a concurrent mark we are going to uncommit memory soon.
58 if (G1CollectedHeap::heap()->concurrent_mark()->cm_thread()->during_cycle()) {
59 log_debug(gc, periodic)("Concurrent cycle in progress. Skipping.");
60 return false;
61 }
62
63 // Check if enough time has passed since the last GC.
64 uintx time_since_last_gc;
65 if ((G1PeriodicGCInterval == 0) ||
66 ((time_since_last_gc = (uintx)Universe::heap()->millis_since_last_gc()) < G1PeriodicGCInterval)) {
67 log_debug(gc, periodic)("Last GC occurred " UINTX_FORMAT "ms earlier which is higher than threshold " UINTX_FORMAT "ms. Skipping.",
68 time_since_last_gc, G1PeriodicGCInterval);
69 return false;
70 }
71
72 // Check if load is lower than max.
73 double recent_load;
74 if ((G1PeriodicGCSystemLoadThreshold > 0) &&
75 (os::loadavg(&recent_load, 1) == -1 || recent_load > G1PeriodicGCSystemLoadThreshold)) {
76 log_debug(gc, periodic)("Load %1.2f is higher than threshold " UINTX_FORMAT ". Skipping.",
77 recent_load, G1PeriodicGCSystemLoadThreshold);
78 return false;
79 }
80
81 return true;
82 }
83
84 void G1YoungRemSetSamplingThread::run_service() {
85 double vtime_start = os::elapsedVTime();
86
87 while (!should_terminate()) {
88 sample_young_list_rs_lengths();
89
90 if (os::supports_vtime()) {
91 _vtime_accum = (os::elapsedVTime() - vtime_start);
92 } else {
93 _vtime_accum = 0.0;
94 }
95
96 if ((os::elapsedTime() - _last_periodic_gc_attempt_s) > (G1PeriodicGCInterval / 1000.0)) {
97 log_debug(gc, periodic)("Checking for periodic GC.");
98 if (should_start_periodic_gc()) {
99 Universe::heap()->collect(GCCause::_g1_periodic_collection);
100 }
101 _last_periodic_gc_attempt_s = os::elapsedTime();
102 }
103
104 sleep_before_next_cycle();
105 }
106 }
107
108 void G1YoungRemSetSamplingThread::stop_service() {
109 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
110 _monitor.notify();
111 }
112
113 class G1YoungRemSetSamplingClosure : public HeapRegionClosure {
114 SuspendibleThreadSetJoiner* _sts;
115 size_t _regions_visited;
116 size_t _sampled_rs_lengths;
117 public:
118 G1YoungRemSetSamplingClosure(SuspendibleThreadSetJoiner* sts) :
119 HeapRegionClosure(), _sts(sts), _regions_visited(0), _sampled_rs_lengths(0) { }
120
121 virtual bool do_heap_region(HeapRegion* r) {
122 size_t rs_length = r->rem_set()->occupied();
123 _sampled_rs_lengths += rs_length;
124
125 // Update the collection set policy information for this region
126 G1CollectedHeap::heap()->collection_set()->update_young_region_prediction(r, rs_length);
127
128 _regions_visited++;
129
130 if (_regions_visited == 10) {
131 if (_sts->should_yield()) {
132 _sts->yield();
133 // A gc may have occurred and our sampling data is stale and further
134 // traversal of the collection set is unsafe
135 return true;
136 }
137 _regions_visited = 0;
138 }
139 return false;
140 }
141
142 size_t sampled_rs_lengths() const { return _sampled_rs_lengths; }
143 };
144
145 void G1YoungRemSetSamplingThread::sample_young_list_rs_lengths() {
146 SuspendibleThreadSetJoiner sts;
147 G1CollectedHeap* g1h = G1CollectedHeap::heap();
148 G1Policy* g1p = g1h->g1_policy();
149
150 if (g1p->adaptive_young_list_length()) {
151 G1YoungRemSetSamplingClosure cl(&sts);
152
153 G1CollectionSet* g1cs = g1h->collection_set();
154 g1cs->iterate(&cl);
155
156 if (cl.is_complete()) {
157 g1p->revise_young_list_target_length_if_necessary(cl.sampled_rs_lengths());
158 }
159 }
160 }