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 In the second case, however, we should stall until 87 // until the GC locker is no longer active and then retry the initial mark GC. 88 _should_retry_gc = true; 89 } 90 } 91 return res; 92 } 93 94 void VM_G1IncCollectionPause::doit() { 95 G1CollectedHeap*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