1 /*
2 * Copyright (c) 2001, 2018, 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/concurrentMarkThread.inline.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1Policy.hpp"
29 #include "gc/shared/gcId.hpp"
30 #include "gc/g1/vm_operations_g1.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/gcTraceTime.inline.hpp"
33 #include "gc/shared/isGCActiveMark.hpp"
34 #include "runtime/interfaceSupport.hpp"
35
36 void VM_G1CollectFull::doit() {
37 G1CollectedHeap* g1h = G1CollectedHeap::heap();
38 GCCauseSetter x(g1h, _gc_cause);
39 g1h->do_full_collection(false /* clear_all_soft_refs */);
40 }
41
42 VM_G1CollectForAllocation::VM_G1CollectForAllocation(size_t word_size,
43 uint gc_count_before,
44 GCCause::Cause gc_cause,
45 bool should_initiate_conc_mark,
46 double target_pause_time_ms,
47 AllocationContext_t allocation_context)
48 : VM_CollectForAllocation(word_size, gc_count_before, gc_cause),
49 _pause_succeeded(false),
50 _allocation_context(allocation_context),
51 _should_initiate_conc_mark(should_initiate_conc_mark),
52 _target_pause_time_ms(target_pause_time_ms),
53 _should_retry_gc(false),
54 _old_marking_cycles_completed_before(0) {
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
61 bool 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
77 void 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 _allocation_context,
86 false /* expect_null_cur_alloc_region */);
87 if (_result != NULL) {
88 // If we can successfully allocate before we actually do the
89 // pause then we will consider this pause successful.
90 _pause_succeeded = true;
91 return;
92 }
93 }
94
95 GCCauseSetter x(g1h, _gc_cause);
96 if (_should_initiate_conc_mark) {
97 // It's safer to read old_marking_cycles_completed() here, given
98 // that noone else will be updating it concurrently. Since we'll
99 // only need it if we're initiating a marking cycle, no point in
100 // setting it earlier.
101 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
102
103 // At this point we are supposed to start a concurrent cycle. We
104 // will do so if one is not already in progress.
105 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
106
107 // The above routine returns true if we were able to force the
108 // next GC pause to be an initial mark; it returns false if a
109 // marking cycle is already in progress.
110 //
111 // If a marking cycle is already in progress just return and skip the
112 // pause below - if the reason for requesting this initial mark pause
113 // was due to a System.gc() then the requesting thread should block in
114 // doit_epilogue() until the marking cycle is complete.
115 //
116 // If this initial mark pause was requested as part of a humongous
117 // allocation then we know that the marking cycle must just have
118 // been started by another thread (possibly also allocating a humongous
119 // object) as there was no active marking cycle when the requesting
120 // thread checked before calling collect() in
121 // attempt_allocation_humongous(). Retrying the GC, in this case,
122 // will cause the requesting thread to spin inside collect() until the
123 // just started marking cycle is complete - which may be a while. So
124 // we do NOT retry the GC.
125 if (!res) {
126 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
127 if (_gc_cause != GCCause::_g1_humongous_allocation) {
128 _should_retry_gc = true;
129 }
130 return;
131 }
132 }
133
134 // Try a partial collection of some kind.
135 _pause_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
136
137 if (_pause_succeeded) {
138 if (_word_size > 0) {
139 // An allocation had been requested. Do it, eventually trying a stronger
140 // kind of GC.
141 _result = g1h->satisfy_failed_allocation(_word_size, _allocation_context, &_pause_succeeded);
142 } else if (!g1h->has_regions_left_for_allocation()) {
143 // There has been a request to perform a GC to free some space. We have no
144 // information on how much memory has been asked for. In case there are
145 // absolutely no regions left to allocate into, do a maximally compacting full GC.
146 log_info(gc, ergo)("Attempting maximally compacting collection");
147 _pause_succeeded = g1h->do_full_collection(false, /* explicit gc */
148 true /* clear_all_soft_refs */);
149 }
150 guarantee(_pause_succeeded, "Elevated collections during the safepoint must always succeed.");
151 } else {
152 assert(_result == NULL, "invariant");
153 // The only reason for the pause to not be successful is that, the GC locker is
154 // active (or has become active since the prologue was executed). In this case
155 // we should retry the pause after waiting for the GC locker to become inactive.
156 _should_retry_gc = true;
157 }
158 }
159
160 void VM_G1CollectForAllocation::doit_epilogue() {
161 VM_CollectForAllocation::doit_epilogue();
162
163 // If the pause was initiated by a System.gc() and
164 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
165 // that just started (or maybe one that was already in progress) to
166 // finish.
167 if (GCCause::is_user_requested_gc(_gc_cause) &&
168 _should_initiate_conc_mark) {
169 assert(ExplicitGCInvokesConcurrent,
170 "the only way to be here is if ExplicitGCInvokesConcurrent is set");
171
172 G1CollectedHeap* g1h = G1CollectedHeap::heap();
173
174 // In the doit() method we saved g1h->old_marking_cycles_completed()
175 // in the _old_marking_cycles_completed_before field. We have to
176 // wait until we observe that g1h->old_marking_cycles_completed()
177 // has increased by at least one. This can happen if a) we started
178 // a cycle and it completes, b) a cycle already in progress
179 // completes, or c) a Full GC happens.
180
181 // If the condition has already been reached, there's no point in
182 // actually taking the lock and doing the wait.
183 if (g1h->old_marking_cycles_completed() <=
184 _old_marking_cycles_completed_before) {
185 // The following is largely copied from CMS
186
187 Thread* thr = Thread::current();
188 assert(thr->is_Java_thread(), "invariant");
189 JavaThread* jt = (JavaThread*)thr;
190 ThreadToNativeFromVM native(jt);
191
192 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
193 while (g1h->old_marking_cycles_completed() <=
194 _old_marking_cycles_completed_before) {
195 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
196 }
197 }
198 }
199 }
200
201 void VM_CGC_Operation::doit() {
202 GCIdMark gc_id_mark(_gc_id);
203 GCTraceCPUTime tcpu;
204 G1CollectedHeap* g1h = G1CollectedHeap::heap();
205 GCTraceTime(Info, gc) t(_printGCMessage, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);
206 IsGCActiveMark x;
207 _cl->do_void();
208 }
209
210 bool VM_CGC_Operation::doit_prologue() {
211 Heap_lock->lock();
212 return true;
213 }
214
215 void VM_CGC_Operation::doit_epilogue() {
216 if (Universe::has_reference_pending_list()) {
217 Heap_lock->notify_all();
218 }
219 Heap_lock->unlock();
220 }