1 /* 2 * Copyright (c) 2001, 2015, 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(uint gc_count_before, 38 size_t word_size) 39 : VM_G1OperationWithAllocRequest(gc_count_before, word_size, 40 GCCause::_allocation_failure) { 41 guarantee(word_size != 0, "An allocation should always be requested with this operation."); 42 } 43 44 void VM_G1CollectForAllocation::doit() { 45 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 46 GCCauseSetter x(g1h, _gc_cause); 47 48 _result = g1h->satisfy_failed_allocation(_word_size, allocation_context(), &_pause_succeeded); 49 assert(_result == NULL || _pause_succeeded, 50 "if we get back a result, the pause should have succeeded"); 51 } 52 53 void VM_G1CollectFull::doit() { 54 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 55 GCCauseSetter x(g1h, _gc_cause); 56 g1h->do_full_collection(false /* clear_all_soft_refs */); 57 } 58 59 VM_G1IncCollectionPause::VM_G1IncCollectionPause(uint gc_count_before, 60 size_t word_size, 61 bool should_initiate_conc_mark, 62 double target_pause_time_ms, 63 GCCause::Cause gc_cause) 64 : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause), 65 _should_initiate_conc_mark(should_initiate_conc_mark), 66 _target_pause_time_ms(target_pause_time_ms), 67 _should_retry_gc(false), 68 _old_marking_cycles_completed_before(0) { 69 guarantee(target_pause_time_ms > 0.0, 70 err_msg("target_pause_time_ms = %1.6lf should be positive", 71 target_pause_time_ms)); 72 _gc_cause = gc_cause; 73 } 74 75 bool VM_G1IncCollectionPause::doit_prologue() { 76 bool res = VM_G1OperationWithAllocRequest::doit_prologue(); 77 if (!res) { 78 if (_should_initiate_conc_mark) { 79 // The prologue can fail for a couple of reasons. The first is that another GC 80 // got scheduled and prevented the scheduling of the initial mark GC. The 81 // second is that the GC locker may be active and the heap can't be expanded. 82 // In both cases we want to retry the GC so that the initial mark pause is 83 // actually scheduled. In the second case, however, we should stall until 84 // until the GC locker is no longer active and then retry the initial mark GC. 85 _should_retry_gc = true; 86 } 87 } 88 return res; 89 } 90 91 void VM_G1IncCollectionPause::doit() { 92 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 93 assert(!_should_initiate_conc_mark || 94 ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) || 95 (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) || 96 _gc_cause == GCCause::_g1_humongous_allocation || 97 _gc_cause == GCCause::_update_allocation_context_stats_inc), 98 "only a GC locker, a System.gc(), stats update or a hum allocation induced GC should start a cycle"); 99 100 if (_word_size > 0) { 101 // An allocation has been requested. So, try to do that first. 102 _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(), 103 false /* expect_null_cur_alloc_region */); 104 if (_result != NULL) { 105 // If we can successfully allocate before we actually do the 106 // pause then we will consider this pause successful. 107 _pause_succeeded = true; 108 return; 109 } 110 } 111 112 GCCauseSetter x(g1h, _gc_cause); 113 if (_should_initiate_conc_mark) { 114 // It's safer to read old_marking_cycles_completed() here, given 115 // that noone else will be updating it concurrently. Since we'll 116 // only need it if we're initiating a marking cycle, no point in 117 // setting it earlier. 118 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed(); 119 120 // At this point we are supposed to start a concurrent cycle. We 121 // will do so if one is not already in progress. 122 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause); 123 124 // The above routine returns true if we were able to force the 125 // next GC pause to be an initial mark; it returns false if a 126 // marking cycle is already in progress. 127 // 128 // If a marking cycle is already in progress just return and skip the 129 // pause below - if the reason for requesting this initial mark pause 130 // was due to a System.gc() then the requesting thread should block in 131 // doit_epilogue() until the marking cycle is complete. 132 // 133 // If this initial mark pause was requested as part of a humongous 134 // allocation then we know that the marking cycle must just have 135 // been started by another thread (possibly also allocating a humongous 136 // object) as there was no active marking cycle when the requesting 137 // thread checked before calling collect() in 138 // attempt_allocation_humongous(). Retrying the GC, in this case, 139 // will cause the requesting thread to spin inside collect() until the 140 // just started marking cycle is complete - which may be a while. So 141 // we do NOT retry the GC. 142 if (!res) { 143 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating"); 144 if (_gc_cause != GCCause::_g1_humongous_allocation) { 145 _should_retry_gc = true; 146 } 147 return; 148 } 149 } 150 151 _pause_succeeded = 152 g1h->do_collection_pause_at_safepoint(_target_pause_time_ms); 153 if (_pause_succeeded && _word_size > 0) { 154 // An allocation had been requested. 155 _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(), 156 true /* expect_null_cur_alloc_region */); 157 } else { 158 assert(_result == NULL, "invariant"); 159 if (!_pause_succeeded) { 160 // Another possible reason reason for the pause to not be successful 161 // is that, again, the GC locker is active (and has become active 162 // since the prologue was executed). In this case we should retry 163 // the pause after waiting for the GC locker to become inactive. 164 _should_retry_gc = true; 165 } 166 } 167 } 168 169 void VM_G1IncCollectionPause::doit_epilogue() { 170 VM_G1OperationWithAllocRequest::doit_epilogue(); 171 172 // If the pause was initiated by a System.gc() and 173 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle 174 // that just started (or maybe one that was already in progress) to 175 // finish. 176 if (GCCause::is_user_requested_gc(_gc_cause) && 177 _should_initiate_conc_mark) { 178 assert(ExplicitGCInvokesConcurrent, 179 "the only way to be here is if ExplicitGCInvokesConcurrent is set"); 180 181 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 182 183 // In the doit() method we saved g1h->old_marking_cycles_completed() 184 // in the _old_marking_cycles_completed_before field. We have to 185 // wait until we observe that g1h->old_marking_cycles_completed() 186 // has increased by at least one. This can happen if a) we started 187 // a cycle and it completes, b) a cycle already in progress 188 // completes, or c) a Full GC happens. 189 190 // If the condition has already been reached, there's no point in 191 // actually taking the lock and doing the wait. 192 if (g1h->old_marking_cycles_completed() <= 193 _old_marking_cycles_completed_before) { 194 // The following is largely copied from CMS 195 196 Thread* thr = Thread::current(); 197 assert(thr->is_Java_thread(), "invariant"); 198 JavaThread* jt = (JavaThread*)thr; 199 ThreadToNativeFromVM native(jt); 200 201 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 202 while (g1h->old_marking_cycles_completed() <= 203 _old_marking_cycles_completed_before) { 204 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 205 } 206 } 207 } 208 } 209 210 void VM_CGC_Operation::acquire_pending_list_lock() { 211 assert(_needs_pll, "don't call this otherwise"); 212 // The caller may block while communicating 213 // with the SLT thread in order to acquire/release the PLL. 214 SurrogateLockerThread* slt = ConcurrentMarkThread::slt(); 215 if (slt != NULL) { 216 slt->manipulatePLL(SurrogateLockerThread::acquirePLL); 217 } else { 218 SurrogateLockerThread::report_missing_slt(); 219 } 220 } 221 222 void VM_CGC_Operation::release_and_notify_pending_list_lock() { 223 assert(_needs_pll, "don't call this otherwise"); 224 // The caller may block while communicating 225 // with the SLT thread in order to acquire/release the PLL. 226 ConcurrentMarkThread::slt()-> 227 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL); 228 } 229 230 void VM_CGC_Operation::doit() { 231 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 232 GCTraceTime t(_printGCMessage, G1Log::fine(), true, G1CollectedHeap::heap()->gc_timer_cm(), G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id()); 233 SharedHeap* sh = SharedHeap::heap(); 234 // This could go away if CollectedHeap gave access to _gc_is_active... 235 if (sh != NULL) { 236 IsGCActiveMark x; 237 _cl->do_void(); 238 } else { 239 _cl->do_void(); 240 } 241 } 242 243 bool VM_CGC_Operation::doit_prologue() { 244 // Note the relative order of the locks must match that in 245 // VM_GC_Operation::doit_prologue() or deadlocks can occur 246 if (_needs_pll) { 247 acquire_pending_list_lock(); 248 } 249 250 Heap_lock->lock(); 251 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true; 252 return true; 253 } 254 255 void VM_CGC_Operation::doit_epilogue() { 256 // Note the relative order of the unlocks must match that in 257 // VM_GC_Operation::doit_epilogue() 258 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false; 259 Heap_lock->unlock(); 260 if (_needs_pll) { 261 release_and_notify_pending_list_lock(); 262 } 263 }