1/*
2 * Copyright (c) 2001, 2016, 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
36VM_G1CollectForAllocation::VM_G1CollectForAllocation(uint gc_count_before,
37                                                     size_t word_size)
38  : VM_G1OperationWithAllocRequest(gc_count_before, word_size,
39                                   GCCause::_allocation_failure) {
40  guarantee(word_size != 0, "An allocation should always be requested with this operation.");
41}
42
43void VM_G1CollectForAllocation::doit() {
44  G1CollectedHeap* g1h = G1CollectedHeap::heap();
45  GCCauseSetter x(g1h, _gc_cause);
46
47  _result = g1h->satisfy_failed_allocation(_word_size, allocation_context(), &_pause_succeeded);
48  assert(_result == NULL || _pause_succeeded,
49         "if we get back a result, the pause should have succeeded");
50}
51
52void VM_G1CollectFull::doit() {
53  G1CollectedHeap* g1h = G1CollectedHeap::heap();
54  GCCauseSetter x(g1h, _gc_cause);
55  g1h->do_full_collection(false /* clear_all_soft_refs */);
56}
57
58VM_G1IncCollectionPause::VM_G1IncCollectionPause(uint           gc_count_before,
59                                                 size_t         word_size,
60                                                 bool           should_initiate_conc_mark,
61                                                 double         target_pause_time_ms,
62                                                 GCCause::Cause gc_cause)
63  : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),
64    _should_initiate_conc_mark(should_initiate_conc_mark),
65    _target_pause_time_ms(target_pause_time_ms),
66    _should_retry_gc(false),
67    _old_marking_cycles_completed_before(0) {
68  guarantee(target_pause_time_ms > 0.0,
69            "target_pause_time_ms = %1.6lf should be positive",
70            target_pause_time_ms);
71  _gc_cause = gc_cause;
72}
73
74bool VM_G1IncCollectionPause::doit_prologue() {
75  bool res = VM_G1OperationWithAllocRequest::doit_prologue();
76  if (!res) {
77    if (_should_initiate_conc_mark) {
78      // The prologue can fail for a couple of reasons. The first is that another GC
79      // got scheduled and prevented the scheduling of the initial mark GC. The
80      // second is that the GC locker may be active and the heap can't be expanded.
81      // In both cases we want to retry the GC so that the initial mark pause is
82      // actually scheduled. In the second case, however, we should stall until
83      // until the GC locker is no longer active and then retry the initial mark GC.
84      _should_retry_gc = true;
85    }
86  }
87  return res;
88}
89
90void VM_G1IncCollectionPause::doit() {
91  G1CollectedHeap* g1h = G1CollectedHeap::heap();
92  assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause),
93      "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle");
94
95  if (_word_size > 0) {
96    // An allocation has been requested. So, try to do that first.
97    _result = g1h->attempt_allocation_at_safepoint(_word_size,
98                                                   allocation_context(),
99                                                   false /* expect_null_cur_alloc_region */);
100    if (_result != NULL) {
101      // If we can successfully allocate before we actually do the
102      // pause then we will consider this pause successful.
103      _pause_succeeded = true;
104      return;
105    }
106  }
107
108  GCCauseSetter x(g1h, _gc_cause);
109  if (_should_initiate_conc_mark) {
110    // It's safer to read old_marking_cycles_completed() here, given
111    // that noone else will be updating it concurrently. Since we'll
112    // only need it if we're initiating a marking cycle, no point in
113    // setting it earlier.
114    _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
115
116    // At this point we are supposed to start a concurrent cycle. We
117    // will do so if one is not already in progress.
118    bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
119
120    // The above routine returns true if we were able to force the
121    // next GC pause to be an initial mark; it returns false if a
122    // marking cycle is already in progress.
123    //
124    // If a marking cycle is already in progress just return and skip the
125    // pause below - if the reason for requesting this initial mark pause
126    // was due to a System.gc() then the requesting thread should block in
127    // doit_epilogue() until the marking cycle is complete.
128    //
129    // If this initial mark pause was requested as part of a humongous
130    // allocation then we know that the marking cycle must just have
131    // been started by another thread (possibly also allocating a humongous
132    // object) as there was no active marking cycle when the requesting
133    // thread checked before calling collect() in
134    // attempt_allocation_humongous(). Retrying the GC, in this case,
135    // will cause the requesting thread to spin inside collect() until the
136    // just started marking cycle is complete - which may be a while. So
137    // we do NOT retry the GC.
138    if (!res) {
139      assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
140      if (_gc_cause != GCCause::_g1_humongous_allocation) {
141        _should_retry_gc = true;
142      }
143      return;
144    }
145  }
146
147  _pause_succeeded =
148    g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
149  if (_pause_succeeded && _word_size > 0) {
150    // An allocation had been requested.
151    _result = g1h->attempt_allocation_at_safepoint(_word_size,
152                                                   allocation_context(),
153                                                   true /* expect_null_cur_alloc_region */);
154  } else {
155    assert(_result == NULL, "invariant");
156    if (!_pause_succeeded) {
157      // Another possible reason reason for the pause to not be successful
158      // is that, again, the GC locker is active (and has become active
159      // since the prologue was executed). In this case we should retry
160      // the pause after waiting for the GC locker to become inactive.
161      _should_retry_gc = true;
162    }
163  }
164}
165
166void VM_G1IncCollectionPause::doit_epilogue() {
167  VM_G1OperationWithAllocRequest::doit_epilogue();
168
169  // If the pause was initiated by a System.gc() and
170  // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
171  // that just started (or maybe one that was already in progress) to
172  // finish.
173  if (GCCause::is_user_requested_gc(_gc_cause) &&
174      _should_initiate_conc_mark) {
175    assert(ExplicitGCInvokesConcurrent,
176           "the only way to be here is if ExplicitGCInvokesConcurrent is set");
177
178    G1CollectedHeap* g1h = G1CollectedHeap::heap();
179
180    // In the doit() method we saved g1h->old_marking_cycles_completed()
181    // in the _old_marking_cycles_completed_before field. We have to
182    // wait until we observe that g1h->old_marking_cycles_completed()
183    // has increased by at least one. This can happen if a) we started
184    // a cycle and it completes, b) a cycle already in progress
185    // completes, or c) a Full GC happens.
186
187    // If the condition has already been reached, there's no point in
188    // actually taking the lock and doing the wait.
189    if (g1h->old_marking_cycles_completed() <=
190                                          _old_marking_cycles_completed_before) {
191      // The following is largely copied from CMS
192
193      Thread* thr = Thread::current();
194      assert(thr->is_Java_thread(), "invariant");
195      JavaThread* jt = (JavaThread*)thr;
196      ThreadToNativeFromVM native(jt);
197
198      MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
199      while (g1h->old_marking_cycles_completed() <=
200                                          _old_marking_cycles_completed_before) {
201        FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
202      }
203    }
204  }
205}
206
207void VM_CGC_Operation::doit() {
208  GCIdMark gc_id_mark(_gc_id);
209  GCTraceCPUTime tcpu;
210  G1CollectedHeap* g1h = G1CollectedHeap::heap();
211  GCTraceTime(Info, gc) t(_printGCMessage, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);
212  IsGCActiveMark x;
213  _cl->do_void();
214}
215
216bool VM_CGC_Operation::doit_prologue() {
217  Heap_lock->lock();
218  return true;
219}
220
221void VM_CGC_Operation::doit_epilogue() {
222  if (Universe::has_reference_pending_list()) {
223    Heap_lock->notify_all();
224  }
225  Heap_lock->unlock();
226}
227