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/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 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 assert(_needs_pll, "don't call this otherwise"); 209 // The caller may block while communicating 210 // with the SLT thread in order to acquire/release the PLL. 211 SurrogateLockerThread* slt = ConcurrentMarkThread::slt(); 212 if (slt != NULL) { 213 slt->manipulatePLL(SurrogateLockerThread::acquirePLL); 214 } else { 215 SurrogateLockerThread::report_missing_slt(); 216 } 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 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 229 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 230 GCTraceTime t(_printGCMessage, G1Log::fine(), true, g1h->gc_timer_cm(), g1h->concurrent_mark()->concurrent_gc_id()); 231 IsGCActiveMark x; 232 _cl->do_void(); 233 } 234 235 bool VM_CGC_Operation::doit_prologue() { 236 // Note the relative order of the locks must match that in 237 // VM_GC_Operation::doit_prologue() or deadlocks can occur 238 if (_needs_pll) { 239 acquire_pending_list_lock(); 240 } 241 242 Heap_lock->lock(); 243 return true; 244 } 245 246 void VM_CGC_Operation::doit_epilogue() { 247 // Note the relative order of the unlocks must match that in 248 // VM_GC_Operation::doit_epilogue() 249 Heap_lock->unlock(); 250 if (_needs_pll) { 251 release_and_notify_pending_list_lock(); 252 } 253 }