vm_operations_g1.cpp revision 8413:92457dfb91bd 
1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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).
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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.
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23 */
24
25#include "precompiled.hpp"
26#include "gc/g1/concurrentMarkThread.inline.hpp"
27#include "gc/g1/g1CollectedHeap.inline.hpp"
28#include "gc/g1/g1CollectorPolicy.hpp"
29#include "gc/g1/g1Log.hpp"
30#include "gc/g1/vm_operations_g1.hpp"
31#include "gc/shared/gcTimer.hpp"
32#include "gc/shared/gcTraceTime.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            err_msg("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, allocation_context(),
98                                     false /* expect_null_cur_alloc_region */);
99    if (_result != NULL) {
100      // If we can successfully allocate before we actually do the
101      // pause then we will consider this pause successful.
102      _pause_succeeded = true;
103      return;
104    }
105  }
106
107  GCCauseSetter x(g1h, _gc_cause);
108  if (_should_initiate_conc_mark) {
109    // It's safer to read old_marking_cycles_completed() here, given
110    // that noone else will be updating it concurrently. Since we'll
111    // only need it if we're initiating a marking cycle, no point in
112    // setting it earlier.
113    _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
114
115    // At this point we are supposed to start a concurrent cycle. We
116    // will do so if one is not already in progress.
117    bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
118
119    // The above routine returns true if we were able to force the
120    // next GC pause to be an initial mark; it returns false if a
121    // marking cycle is already in progress.
122    //
123    // If a marking cycle is already in progress just return and skip the
124    // pause below - if the reason for requesting this initial mark pause
125    // was due to a System.gc() then the requesting thread should block in
126    // doit_epilogue() until the marking cycle is complete.
127    //
128    // If this initial mark pause was requested as part of a humongous
129    // allocation then we know that the marking cycle must just have
130    // been started by another thread (possibly also allocating a humongous
131    // object) as there was no active marking cycle when the requesting
132    // thread checked before calling collect() in
133    // attempt_allocation_humongous(). Retrying the GC, in this case,
134    // will cause the requesting thread to spin inside collect() until the
135    // just started marking cycle is complete - which may be a while. So
136    // we do NOT retry the GC.
137    if (!res) {
138      assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
139      if (_gc_cause != GCCause::_g1_humongous_allocation) {
140        _should_retry_gc = true;
141      }
142      return;
143    }
144  }
145
146  _pause_succeeded =
147    g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
148  if (_pause_succeeded && _word_size > 0) {
149    // An allocation had been requested.
150    _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),
151                                      true /* expect_null_cur_alloc_region */);
152  } else {
153    assert(_result == NULL, "invariant");
154    if (!_pause_succeeded) {
155      // Another possible reason reason for the pause to not be successful
156      // is that, again, the GC locker is active (and has become active
157      // since the prologue was executed). In this case we should retry
158      // the pause after waiting for the GC locker to become inactive.
159      _should_retry_gc = true;
160    }
161  }
162}
163
164void VM_G1IncCollectionPause::doit_epilogue() {
165  VM_G1OperationWithAllocRequest::doit_epilogue();
166
167  // If the pause was initiated by a System.gc() and
168  // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
169  // that just started (or maybe one that was already in progress) to
170  // finish.
171  if (_gc_cause == GCCause::_java_lang_system_gc &&
172      _should_initiate_conc_mark) {
173    assert(ExplicitGCInvokesConcurrent,
174           "the only way to be here is if ExplicitGCInvokesConcurrent is set");
175
176    G1CollectedHeap* g1h = G1CollectedHeap::heap();
177
178    // In the doit() method we saved g1h->old_marking_cycles_completed()
179    // in the _old_marking_cycles_completed_before field. We have to
180    // wait until we observe that g1h->old_marking_cycles_completed()
181    // has increased by at least one. This can happen if a) we started
182    // a cycle and it completes, b) a cycle already in progress
183    // completes, or c) a Full GC happens.
184
185    // If the condition has already been reached, there's no point in
186    // actually taking the lock and doing the wait.
187    if (g1h->old_marking_cycles_completed() <=
188                                          _old_marking_cycles_completed_before) {
189      // The following is largely copied from CMS
190
191      Thread* thr = Thread::current();
192      assert(thr->is_Java_thread(), "invariant");
193      JavaThread* jt = (JavaThread*)thr;
194      ThreadToNativeFromVM native(jt);
195
196      MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
197      while (g1h->old_marking_cycles_completed() <=
198                                          _old_marking_cycles_completed_before) {
199        FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
200      }
201    }
202  }
203}
204
205void VM_CGC_Operation::acquire_pending_list_lock() {
206  assert(_needs_pll, "don't call this otherwise");
207  // The caller may block while communicating
208  // with the SLT thread in order to acquire/release the PLL.
209  SurrogateLockerThread* slt = ConcurrentMarkThread::slt();
210  if (slt != NULL) {
211    slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
212  } else {
213    SurrogateLockerThread::report_missing_slt();
214  }
215}
216
217void VM_CGC_Operation::release_and_notify_pending_list_lock() {
218  assert(_needs_pll, "don't call this otherwise");
219  // The caller may block while communicating
220  // with the SLT thread in order to acquire/release the PLL.
221  ConcurrentMarkThread::slt()->
222    manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
223}
224
225void VM_CGC_Operation::doit() {
226  TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
227  G1CollectedHeap* g1h = G1CollectedHeap::heap();
228  GCTraceTime t(_printGCMessage, G1Log::fine(), true, g1h->gc_timer_cm(), g1h->concurrent_mark()->concurrent_gc_id());
229  IsGCActiveMark x;
230  _cl->do_void();
231}
232
233bool VM_CGC_Operation::doit_prologue() {
234  // Note the relative order of the locks must match that in
235  // VM_GC_Operation::doit_prologue() or deadlocks can occur
236  if (_needs_pll) {
237    acquire_pending_list_lock();
238  }
239
240  Heap_lock->lock();
241  return true;
242}
243
244void VM_CGC_Operation::doit_epilogue() {
245  // Note the relative order of the unlocks must match that in
246  // VM_GC_Operation::doit_epilogue()
247  Heap_lock->unlock();
248  if (_needs_pll) {
249    release_and_notify_pending_list_lock();
250  }
251}
252