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/g1CollectorPolicy.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 VM_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 
  43 void 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 
  52 void 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 
  58 VM_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 
  74 bool 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 
  90 void 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 
 166 void 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 
 207 void VM_CGC_Operation::acquire_pending_list_lock() {
 208   _pending_list_locker.lock();
 209 }
 210 
 211 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
 212   _pending_list_locker.unlock();
 213 }
 214 
 215 void VM_CGC_Operation::doit() {
 216   GCIdMark gc_id_mark(_gc_id);
 217   GCTraceCPUTime tcpu;
 218   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 219   GCTraceTime(Info, gc) t(_printGCMessage, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);
 220   TraceCollectorStats tcs(g1h->g1mm()->conc_collection_counters());
 221   SvcGCMarker sgcm(SvcGCMarker::CONCURRENT);
 222   IsGCActiveMark x;
 223   _cl->do_void();
 224 }
 225 
 226 bool VM_CGC_Operation::doit_prologue() {
 227   // Note the relative order of the locks must match that in
 228   // VM_GC_Operation::doit_prologue() or deadlocks can occur
 229   if (_needs_pending_list_lock) {
 230     acquire_pending_list_lock();
 231   }
 232   Heap_lock->lock();
 233   return true;
 234 }
 235 
 236 void VM_CGC_Operation::doit_epilogue() {
 237   // Note the relative order of the unlocks must match that in
 238   // VM_GC_Operation::doit_epilogue()
 239   Heap_lock->unlock();
 240   if (_needs_pending_list_lock) {
 241     release_and_notify_pending_list_lock();
 242   }
 243 }