1 /*
   2  * Copyright (c) 2001, 2012, 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_implementation/g1/concurrentMarkThread.inline.hpp"
  27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  29 #include "gc_implementation/g1/g1Log.hpp"
  30 #include "gc_implementation/g1/vm_operations_g1.hpp"
  31 #include "gc_implementation/shared/isGCActiveMark.hpp"
  32 #include "gc_implementation/g1/vm_operations_g1.hpp"
  33 #include "runtime/interfaceSupport.hpp"
  34 
  35 VM_G1CollectForAllocation::VM_G1CollectForAllocation(
  36                                                   unsigned int 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");
  41 }
  42 
  43 void VM_G1CollectForAllocation::doit() {
  44   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  45   GCCauseSetter x(g1h, _gc_cause);
  46   _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded);
  47   assert(_result == NULL || _pause_succeeded,
  48          "if we get back a result, the pause should have succeeded");
  49 }
  50 
  51 void VM_G1CollectFull::doit() {
  52   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  53   GCCauseSetter x(g1h, _gc_cause);
  54   g1h->do_full_collection(false /* clear_all_soft_refs */);
  55 }
  56 
  57 VM_G1IncCollectionPause::VM_G1IncCollectionPause(
  58                                       unsigned int   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   guarantee(word_size == 0 || gc_cause == GCCause::_g1_inc_collection_pause,
  72             "we can only request an allocation if the GC cause is for "
  73             "an incremental GC pause");
  74   _gc_cause = gc_cause;
  75 }
  76 
  77 bool VM_G1IncCollectionPause::doit_prologue() {
  78   bool res = VM_GC_Operation::doit_prologue();
  79   if (!res) {
  80     if (_should_initiate_conc_mark) {
  81       // The prologue can fail for a couple of reasons. The first is that another GC
  82       // got scheduled and prevented the scheduling of the initial mark GC. The
  83       // second is that the GC locker may be active and the heap can't be expanded.
  84       // In both cases we want to retry the GC so that the initial mark pause is
  85       // actually scheduled. In the second case, however, we should stall until
  86       // until the GC locker is no longer active and then retry the initial mark GC.
  87       _should_retry_gc = true;
  88     }
  89   }
  90   return res;
  91 }
  92 
  93 void VM_G1IncCollectionPause::doit() {
  94   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  95   assert(!_should_initiate_conc_mark ||
  96   ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
  97    (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) ||
  98     _gc_cause == GCCause::_g1_humongous_allocation),
  99          "only a GC locker, a System.gc() or a hum allocation induced GC should start a cycle");
 100 
 101   if (_word_size > 0) {
 102     // An allocation has been requested. So, try to do that first.
 103     _result = g1h->attempt_allocation_at_safepoint(_word_size,
 104                                      false /* expect_null_cur_alloc_region */);
 105     if (_result != NULL) {
 106       // If we can successfully allocate before we actually do the
 107       // pause then we will consider this pause successful.
 108       _pause_succeeded = true;
 109       return;
 110     }
 111   }
 112 
 113   GCCauseSetter x(g1h, _gc_cause);
 114   if (_should_initiate_conc_mark) {
 115     // It's safer to read old_marking_cycles_completed() here, given
 116     // that noone else will be updating it concurrently. Since we'll
 117     // only need it if we're initiating a marking cycle, no point in
 118     // setting it earlier.
 119     _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
 120 
 121     // At this point we are supposed to start a concurrent cycle. We
 122     // will do so if one is not already in progress.
 123     bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
 124 
 125     // The above routine returns true if we were able to force the
 126     // next GC pause to be an initial mark; it returns false if a
 127     // marking cycle is already in progress.
 128     //
 129     // If a marking cycle is already in progress just return and skip the
 130     // pause below - if the reason for requesting this initial mark pause
 131     // was due to a System.gc() then the requesting thread should block in
 132     // doit_epilogue() until the marking cycle is complete.
 133     //
 134     // If this initial mark pause was requested as part of a humongous
 135     // allocation then we know that the marking cycle must just have
 136     // been started by another thread (possibly also allocating a humongous
 137     // object) as there was no active marking cycle when the requesting
 138     // thread checked before calling collect() in
 139     // attempt_allocation_humongous(). Retrying the GC, in this case,
 140     // will cause the requesting thread to spin inside collect() until the
 141     // just started marking cycle is complete - which may be a while. So
 142     // we do NOT retry the GC.
 143     if (!res) {
 144       assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
 145       if (_gc_cause != GCCause::_g1_humongous_allocation) {
 146         _should_retry_gc = true;
 147       }
 148       return;
 149     }
 150   }
 151 
 152   _pause_succeeded =
 153     g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
 154   if (_pause_succeeded && _word_size > 0) {
 155     // An allocation had been requested.
 156     _result = g1h->attempt_allocation_at_safepoint(_word_size,
 157                                       true /* expect_null_cur_alloc_region */);
 158   } else {
 159     assert(_result == NULL, "invariant");
 160     if (!_pause_succeeded) {
 161       // Another possible reason reason for the pause to not be successful
 162       // is that, again, the GC locker is active (and has become active
 163       // since the prologue was executed). In this case we should retry
 164       // the pause after waiting for the GC locker to become inactive.
 165       _should_retry_gc = true;
 166     }
 167   }
 168 }
 169 
 170 void VM_G1IncCollectionPause::doit_epilogue() {
 171   VM_GC_Operation::doit_epilogue();
 172 
 173   // If the pause was initiated by a System.gc() and
 174   // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
 175   // that just started (or maybe one that was already in progress) to
 176   // finish.
 177   if (_gc_cause == GCCause::_java_lang_system_gc &&
 178       _should_initiate_conc_mark) {
 179     assert(ExplicitGCInvokesConcurrent,
 180            "the only way to be here is if ExplicitGCInvokesConcurrent is set");
 181 
 182     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 183 
 184     // In the doit() method we saved g1h->old_marking_cycles_completed()
 185     // in the _old_marking_cycles_completed_before field. We have to
 186     // wait until we observe that g1h->old_marking_cycles_completed()
 187     // has increased by at least one. This can happen if a) we started
 188     // a cycle and it completes, b) a cycle already in progress
 189     // completes, or c) a Full GC happens.
 190 
 191     // If the condition has already been reached, there's no point in
 192     // actually taking the lock and doing the wait.
 193     if (g1h->old_marking_cycles_completed() <=
 194                                           _old_marking_cycles_completed_before) {
 195       // The following is largely copied from CMS
 196 
 197       Thread* thr = Thread::current();
 198       assert(thr->is_Java_thread(), "invariant");
 199       JavaThread* jt = (JavaThread*)thr;
 200       ThreadToNativeFromVM native(jt);
 201 
 202       MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 203       while (g1h->old_marking_cycles_completed() <=
 204                                           _old_marking_cycles_completed_before) {
 205         FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
 206       }
 207     }
 208   }
 209 }
 210 
 211 void VM_CGC_Operation::acquire_pending_list_lock() {
 212   assert(_needs_pll, "don't call this otherwise");
 213   // The caller may block while communicating
 214   // with the SLT thread in order to acquire/release the PLL.
 215   ConcurrentMarkThread::slt()->
 216     manipulatePLL(SurrogateLockerThread::acquirePLL);
 217 }
 218 
 219 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
 220   assert(_needs_pll, "don't call this otherwise");
 221   // The caller may block while communicating
 222   // with the SLT thread in order to acquire/release the PLL.
 223   ConcurrentMarkThread::slt()->
 224     manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
 225 }
 226 
 227 void VM_CGC_Operation::doit() {
 228   gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
 229   TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
 230   TraceTime t(_printGCMessage, G1Log::fine(), true, gclog_or_tty);
 231   SharedHeap* sh = SharedHeap::heap();
 232   // This could go away if CollectedHeap gave access to _gc_is_active...
 233   if (sh != NULL) {
 234     IsGCActiveMark x;
 235     _cl->do_void();
 236   } else {
 237     _cl->do_void();
 238   }
 239 }
 240 
 241 bool VM_CGC_Operation::doit_prologue() {
 242   // Note the relative order of the locks must match that in
 243   // VM_GC_Operation::doit_prologue() or deadlocks can occur
 244   if (_needs_pll) {
 245     acquire_pending_list_lock();
 246   }
 247 
 248   Heap_lock->lock();
 249   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
 250   return true;
 251 }
 252 
 253 void VM_CGC_Operation::doit_epilogue() {
 254   // Note the relative order of the unlocks must match that in
 255   // VM_GC_Operation::doit_epilogue()
 256   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;
 257   Heap_lock->unlock();
 258   if (_needs_pll) {
 259     release_and_notify_pending_list_lock();
 260   }
 261 }