1/*
2 * Copyright (c) 2001, 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.
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23 */
24
25#include "precompiled.hpp"
26#include "gc/g1/g1CollectedHeap.inline.hpp"
27#include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
28#include "gc/g1/g1Policy.hpp"
29#include "gc/g1/g1VMOperations.hpp"
30#include "gc/shared/gcId.hpp"
31#include "gc/shared/gcTimer.hpp"
32#include "gc/shared/gcTraceTime.inline.hpp"
33#include "gc/shared/isGCActiveMark.hpp"
34#include "memory/universe.hpp"
35#include "runtime/interfaceSupport.inline.hpp"
36
37void VM_G1CollectFull::doit() {
38 G1CollectedHeap* g1h = G1CollectedHeap::heap();
39 GCCauseSetter x(g1h, _gc_cause);
40 _gc_succeeded = g1h->do_full_collection(true /* explicit_gc */, false /* clear_all_soft_refs */);
41}
42
43VM_G1CollectForAllocation::VM_G1CollectForAllocation(size_t word_size,
44 uint gc_count_before,
45 GCCause::Cause gc_cause,
46 bool should_initiate_conc_mark,
47 double target_pause_time_ms) :
48 VM_CollectForAllocation(word_size, gc_count_before, gc_cause),
49 _gc_succeeded(false),
50 _should_initiate_conc_mark(should_initiate_conc_mark),
51 _should_retry_gc(false),
52 _target_pause_time_ms(target_pause_time_ms),
53 _old_marking_cycles_completed_before(0) {
54
55 guarantee(target_pause_time_ms > 0.0,
56 "target_pause_time_ms = %1.6lf should be positive",
57 target_pause_time_ms);
58 _gc_cause = gc_cause;
59}
60
61bool VM_G1CollectForAllocation::doit_prologue() {
62 bool res = VM_CollectForAllocation::doit_prologue();
63 if (!res) {
64 if (_should_initiate_conc_mark) {
65 // The prologue can fail for a couple of reasons. The first is that another GC
66 // got scheduled and prevented the scheduling of the initial mark GC. The
67 // second is that the GC locker may be active and the heap can't be expanded.
68 // In both cases we want to retry the GC so that the initial mark pause is
69 // actually scheduled. In the second case, however, we should stall until
70 // until the GC locker is no longer active and then retry the initial mark GC.
71 _should_retry_gc = true;
72 }
73 }
74 return res;
75}
76
77void VM_G1CollectForAllocation::doit() {
78 G1CollectedHeap* g1h = G1CollectedHeap::heap();
79 assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause),
80 "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle");
81
82 if (_word_size > 0) {
83 // An allocation has been requested. So, try to do that first.
84 _result = g1h->attempt_allocation_at_safepoint(_word_size,
85 false /* expect_null_cur_alloc_region */);
86 if (_result != NULL) {
87 // If we can successfully allocate before we actually do the
88 // pause then we will consider this pause successful.
89 _gc_succeeded = true;
90 return;
91 }
92 }
93
94 GCCauseSetter x(g1h, _gc_cause);
95 if (_should_initiate_conc_mark) {
96 // It's safer to read old_marking_cycles_completed() here, given
97 // that noone else will be updating it concurrently. Since we'll
98 // only need it if we're initiating a marking cycle, no point in
99 // setting it earlier.
100 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
101
102 // At this point we are supposed to start a concurrent cycle. We
103 // will do so if one is not already in progress.
104 bool res = g1h->policy()->force_initial_mark_if_outside_cycle(_gc_cause);
105
106 // The above routine returns true if we were able to force the
107 // next GC pause to be an initial mark; it returns false if a
108 // marking cycle is already in progress.
109 //
110 // If a marking cycle is already in progress just return and skip the
111 // pause below - if the reason for requesting this initial mark pause
112 // was due to a System.gc() then the requesting thread should block in
113 // doit_epilogue() until the marking cycle is complete.
114 //
115 // If this initial mark pause was requested as part of a humongous
116 // allocation then we know that the marking cycle must just have
117 // been started by another thread (possibly also allocating a humongous
118 // object) as there was no active marking cycle when the requesting
119 // thread checked before calling collect() in
120 // attempt_allocation_humongous(). Retrying the GC, in this case,
121 // will cause the requesting thread to spin inside collect() until the
122 // just started marking cycle is complete - which may be a while. So
123 // we do NOT retry the GC.
124 if (!res) {
125 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
126 if (_gc_cause != GCCause::_g1_humongous_allocation) {
127 _should_retry_gc = true;
128 }
129 return;
130 }
131 }
132
133 // Try a partial collection of some kind.
134 _gc_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
135
136 if (_gc_succeeded) {
137 if (_word_size > 0) {
138 // An allocation had been requested. Do it, eventually trying a stronger
139 // kind of GC.
140 _result = g1h->satisfy_failed_allocation(_word_size, &_gc_succeeded);
141 } else {
142 bool should_upgrade_to_full = g1h->should_upgrade_to_full_gc(_gc_cause);
143
144 if (should_upgrade_to_full) {
145 // There has been a request to perform a GC to free some space. We have no
146 // information on how much memory has been asked for. In case there are
147 // absolutely no regions left to allocate into, do a maximally compacting full GC.
148 log_info(gc, ergo)("Attempting maximally compacting collection");
149 _gc_succeeded = g1h->do_full_collection(false, /* explicit gc */
150 true /* clear_all_soft_refs */);
151 }
152 }
153 guarantee(_gc_succeeded, "Elevated collections during the safepoint must always succeed.");
154 } else {
155 assert(_result == NULL, "invariant");
156 // The only reason for the pause to not be successful is that, the GC locker is
157 // active (or has become active since the prologue was executed). In this case
158 // we should retry the pause after waiting for the GC locker to become inactive.
159 _should_retry_gc = true;
160 }
161}
162
163void VM_G1CollectForAllocation::doit_epilogue() {
164 VM_CollectForAllocation::doit_epilogue();
165
166 // If the pause was initiated by a System.gc() and
167 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
168 // that just started (or maybe one that was already in progress) to
169 // finish.
170 if (GCCause::is_user_requested_gc(_gc_cause) &&
171 _should_initiate_conc_mark) {
172 assert(ExplicitGCInvokesConcurrent,
173 "the only way to be here is if ExplicitGCInvokesConcurrent is set");
174
175 G1CollectedHeap* g1h = G1CollectedHeap::heap();
176
177 // In the doit() method we saved g1h->old_marking_cycles_completed()
178 // in the _old_marking_cycles_completed_before field. We have to
179 // wait until we observe that g1h->old_marking_cycles_completed()
180 // has increased by at least one. This can happen if a) we started
181 // a cycle and it completes, b) a cycle already in progress
182 // completes, or c) a Full GC happens.
183
184 // If the condition has already been reached, there's no point in
185 // actually taking the lock and doing the wait.
186 if (g1h->old_marking_cycles_completed() <=
187 _old_marking_cycles_completed_before) {
188 // The following is largely copied from CMS
189
190 Thread* thr = Thread::current();
191 assert(thr->is_Java_thread(), "invariant");
192 JavaThread* jt = (JavaThread*)thr;
193 ThreadToNativeFromVM native(jt);
194
195 MonitorLocker ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
196 while (g1h->old_marking_cycles_completed() <=
197 _old_marking_cycles_completed_before) {
198 ml.wait();
199 }
200 }
201 }
202}
203
204void VM_G1Concurrent::doit() {
205 GCIdMark gc_id_mark(_gc_id);
206 GCTraceCPUTime tcpu;
207 G1CollectedHeap* g1h = G1CollectedHeap::heap();
208 GCTraceTime(Info, gc) t(_message, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);
209 TraceCollectorStats tcs(g1h->g1mm()->conc_collection_counters());
210 SvcGCMarker sgcm(SvcGCMarker::CONCURRENT);
211 IsGCActiveMark x;
212 _cl->do_void();
213}
214
215bool VM_G1Concurrent::doit_prologue() {
216 Heap_lock->lock();
217 return true;
218}
219
220void VM_G1Concurrent::doit_epilogue() {
221 if (Universe::has_reference_pending_list()) {
222 Heap_lock->notify_all();
223 }
224 Heap_lock->unlock();
225}
226