1 /*
   2  * Copyright (c) 2001, 2013, 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/gcTimer.hpp"
  32 #include "gc_implementation/shared/gcTraceTime.hpp"
  33 #include "gc_implementation/shared/isGCActiveMark.hpp"
  34 #include "gc_implementation/g1/vm_operations_g1.hpp"
  35 #include "runtime/interfaceSupport.hpp"
  36 
  37 VM_G1CollectForAllocation::VM_G1CollectForAllocation(
  38                                                   unsigned int gc_count_before,
  39                                                   size_t word_size)
  40   : VM_G1OperationWithAllocRequest(gc_count_before, word_size,
  41                                    GCCause::_allocation_failure) {
  42   guarantee(word_size > 0, "an allocation should always be requested");
  43 }
  44 
  45 void VM_G1CollectForAllocation::doit() {
  46   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  47   GCCauseSetter x(g1h, _gc_cause);
  48 
  49   _result = g1h->satisfy_failed_allocation(_word_size, allocation_context(), &_pause_succeeded);
  50   assert(_result == NULL || _pause_succeeded,
  51          "if we get back a result, the pause should have succeeded");
  52 }
  53 
  54 void VM_G1CollectFull::doit() {
  55   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  56   GCCauseSetter x(g1h, _gc_cause);
  57   g1h->do_full_collection(false /* clear_all_soft_refs */);
  58 }
  59 
  60 VM_G1IncCollectionPause::VM_G1IncCollectionPause(
  61                                       unsigned int   gc_count_before,
  62                                       size_t         word_size,
  63                                       bool           should_initiate_conc_mark,
  64                                       double         target_pause_time_ms,
  65                                       GCCause::Cause gc_cause)
  66   : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),
  67     _should_initiate_conc_mark(should_initiate_conc_mark),
  68     _target_pause_time_ms(target_pause_time_ms),
  69     _should_retry_gc(false),
  70     _old_marking_cycles_completed_before(0) {
  71   guarantee(target_pause_time_ms > 0.0,
  72             err_msg("target_pause_time_ms = %1.6lf should be positive",
  73                     target_pause_time_ms));
  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     _gc_cause == GCCause::_update_allocation_context_stats_inc),
 100       "only a GC locker, a System.gc(), stats update or a hum allocation induced GC should start a cycle");
 101 
 102   if (_word_size > 0) {
 103     // An allocation has been requested. So, try to do that first.
 104     _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),
 105                                      false /* expect_null_cur_alloc_region */);
 106     if (_result != NULL) {
 107       // If we can successfully allocate before we actually do the
 108       // pause then we will consider this pause successful.
 109       _pause_succeeded = true;
 110       return;
 111     }
 112   }
 113 
 114   GCCauseSetter x(g1h, _gc_cause);
 115   if (_should_initiate_conc_mark) {
 116     // It's safer to read old_marking_cycles_completed() here, given
 117     // that noone else will be updating it concurrently. Since we'll
 118     // only need it if we're initiating a marking cycle, no point in
 119     // setting it earlier.
 120     _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
 121 
 122     // At this point we are supposed to start a concurrent cycle. We
 123     // will do so if one is not already in progress.
 124     bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
 125 
 126     // The above routine returns true if we were able to force the
 127     // next GC pause to be an initial mark; it returns false if a
 128     // marking cycle is already in progress.
 129     //
 130     // If a marking cycle is already in progress just return and skip the
 131     // pause below - if the reason for requesting this initial mark pause
 132     // was due to a System.gc() then the requesting thread should block in
 133     // doit_epilogue() until the marking cycle is complete.
 134     //
 135     // If this initial mark pause was requested as part of a humongous
 136     // allocation then we know that the marking cycle must just have
 137     // been started by another thread (possibly also allocating a humongous
 138     // object) as there was no active marking cycle when the requesting
 139     // thread checked before calling collect() in
 140     // attempt_allocation_humongous(). Retrying the GC, in this case,
 141     // will cause the requesting thread to spin inside collect() until the
 142     // just started marking cycle is complete - which may be a while. So
 143     // we do NOT retry the GC.
 144     if (!res) {
 145       assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
 146       if (_gc_cause != GCCause::_g1_humongous_allocation) {
 147         _should_retry_gc = true;
 148       }
 149       return;
 150     }
 151   }
 152 
 153   _pause_succeeded =
 154     g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
 155   if (_pause_succeeded && _word_size > 0) {
 156     // An allocation had been requested.
 157     _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),
 158                                       true /* expect_null_cur_alloc_region */);
 159   } else {
 160     assert(_result == NULL, "invariant");
 161     if (!_pause_succeeded) {
 162       // Another possible reason reason for the pause to not be successful
 163       // is that, again, the GC locker is active (and has become active
 164       // since the prologue was executed). In this case we should retry
 165       // the pause after waiting for the GC locker to become inactive.
 166       _should_retry_gc = true;
 167     }
 168   }
 169 }
 170 
 171 void VM_G1IncCollectionPause::doit_epilogue() {
 172   VM_GC_Operation::doit_epilogue();
 173 
 174   // If the pause was initiated by a System.gc() and
 175   // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
 176   // that just started (or maybe one that was already in progress) to
 177   // finish.
 178   if (_gc_cause == GCCause::_java_lang_system_gc &&
 179       _should_initiate_conc_mark) {
 180     assert(ExplicitGCInvokesConcurrent,
 181            "the only way to be here is if ExplicitGCInvokesConcurrent is set");
 182 
 183     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 184 
 185     // In the doit() method we saved g1h->old_marking_cycles_completed()
 186     // in the _old_marking_cycles_completed_before field. We have to
 187     // wait until we observe that g1h->old_marking_cycles_completed()
 188     // has increased by at least one. This can happen if a) we started
 189     // a cycle and it completes, b) a cycle already in progress
 190     // completes, or c) a Full GC happens.
 191 
 192     // If the condition has already been reached, there's no point in
 193     // actually taking the lock and doing the wait.
 194     if (g1h->old_marking_cycles_completed() <=
 195                                           _old_marking_cycles_completed_before) {
 196       // The following is largely copied from CMS
 197 
 198       Thread* thr = Thread::current();
 199       assert(thr->is_Java_thread(), "invariant");
 200       JavaThread* jt = (JavaThread*)thr;
 201       ThreadToNativeFromVM native(jt);
 202 
 203       MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 204       while (g1h->old_marking_cycles_completed() <=
 205                                           _old_marking_cycles_completed_before) {
 206         FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
 207       }
 208     }
 209   }
 210 }
 211 
 212 void VM_CGC_Operation::acquire_pending_list_lock() {
 213   assert(_needs_pll, "don't call this otherwise");
 214   // The caller may block while communicating
 215   // with the SLT thread in order to acquire/release the PLL.
 216   SurrogateLockerThread* slt = ConcurrentMarkThread::slt();
 217   if (slt != NULL) {
 218     slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
 219   } else {
 220     SurrogateLockerThread::report_missing_slt();
 221   }
 222 }
 223 
 224 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
 225   assert(_needs_pll, "don't call this otherwise");
 226   // The caller may block while communicating
 227   // with the SLT thread in order to acquire/release the PLL.
 228   ConcurrentMarkThread::slt()->
 229     manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
 230 }
 231 
 232 void VM_CGC_Operation::doit() {
 233   TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
 234   GCTraceTime t(_printGCMessage, G1Log::fine(), true, G1CollectedHeap::heap()->gc_timer_cm(), G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id());
 235   SharedHeap* sh = SharedHeap::heap();
 236   // This could go away if CollectedHeap gave access to _gc_is_active...
 237   if (sh != NULL) {
 238     IsGCActiveMark x;
 239     _cl->do_void();
 240   } else {
 241     _cl->do_void();
 242   }
 243 }
 244 
 245 bool VM_CGC_Operation::doit_prologue() {
 246   // Note the relative order of the locks must match that in
 247   // VM_GC_Operation::doit_prologue() or deadlocks can occur
 248   if (_needs_pll) {
 249     acquire_pending_list_lock();
 250   }
 251 
 252   Heap_lock->lock();
 253   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
 254   return true;
 255 }
 256 
 257 void VM_CGC_Operation::doit_epilogue() {
 258   // Note the relative order of the unlocks must match that in
 259   // VM_GC_Operation::doit_epilogue()
 260   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;
 261   Heap_lock->unlock();
 262   if (_needs_pll) {
 263     release_and_notify_pending_list_lock();
 264   }
 265 }