1 /* 2 * Copyright (c) 2001, 2019, 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/g1CollectedHeap.inline.hpp" 27 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 28 #include "gc/g1/g1Policy.hpp" 29 #include "gc/g1/g1VMOperations.hpp" 30 #include "gc/shared/gcId.hpp" 31 #include "gc/shared/gcTimer.hpp" 32 #include "gc/shared/gcTraceTime.inline.hpp" 33 #include "gc/shared/isGCActiveMark.hpp" 34 #include "runtime/interfaceSupport.inline.hpp" 35 36 void VM_G1CollectFull::doit() { 37 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 38 GCCauseSetter x(g1h, _gc_cause); 39 _pause_succeeded = g1h->do_full_collection(true /* explicit_gc */, false /* clear_all_soft_refs */); 40 } 41 42 VM_G1CollectForAllocation::VM_G1CollectForAllocation(size_t word_size, 43 uint gc_count_before, 44 GCCause::Cause gc_cause, 45 bool should_initiate_conc_mark, 46 double target_pause_time_ms) : 47 VM_CollectForAllocation(word_size, gc_count_before, gc_cause), 48 _pause_succeeded(false), 49 _should_initiate_conc_mark(should_initiate_conc_mark), 50 _should_retry_gc(false), 51 _target_pause_time_ms(target_pause_time_ms), 52 _old_marking_cycles_completed_before(0) { 53 54 guarantee(target_pause_time_ms > 0.0, 55 "target_pause_time_ms = %1.6lf should be positive", 56 target_pause_time_ms); 57 _gc_cause = gc_cause; 58 } 59 60 bool VM_G1CollectForAllocation::doit_prologue() { 61 bool res = VM_CollectForAllocation::doit_prologue(); 62 if (!res) { 63 if (_should_initiate_conc_mark) { 64 // The prologue can fail for a couple of reasons. The first is that another GC 65 // got scheduled and prevented the scheduling of the initial mark GC. The 66 // second is that the GC locker may be active and the heap can't be expanded. 67 // In both cases we want to retry the GC so that the initial mark pause is 68 // actually scheduled. In the second case, however, we should stall until 69 // until the GC locker is no longer active and then retry the initial mark GC. 70 _should_retry_gc = true; 71 } 72 } 73 return res; 74 } 75 76 void VM_G1CollectForAllocation::doit() { 77 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 78 assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause), 79 "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle"); 80 81 if (_word_size > 0) { 82 // An allocation has been requested. So, try to do that first. 83 _result = g1h->attempt_allocation_at_safepoint(_word_size, 84 false /* expect_null_cur_alloc_region */); 85 if (_result != NULL) { 86 // If we can successfully allocate before we actually do the 87 // pause then we will consider this pause successful. 88 _pause_succeeded = true; 89 return; 90 } 91 } 92 93 GCCauseSetter x(g1h, _gc_cause); 94 if (_should_initiate_conc_mark) { 95 // It's safer to read old_marking_cycles_completed() here, given 96 // that noone else will be updating it concurrently. Since we'll 97 // only need it if we're initiating a marking cycle, no point in 98 // setting it earlier. 99 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed(); 100 101 // At this point we are supposed to start a concurrent cycle. We 102 // will do so if one is not already in progress. 103 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause); 104 105 // The above routine returns true if we were able to force the 106 // next GC pause to be an initial mark; it returns false if a 107 // marking cycle is already in progress. 108 // 109 // If a marking cycle is already in progress just return and skip the 110 // pause below - if the reason for requesting this initial mark pause 111 // was due to a System.gc() then the requesting thread should block in 112 // doit_epilogue() until the marking cycle is complete. 113 // 114 // If this initial mark pause was requested as part of a humongous 115 // allocation then we know that the marking cycle must just have 116 // been started by another thread (possibly also allocating a humongous 117 // object) as there was no active marking cycle when the requesting 118 // thread checked before calling collect() in 119 // attempt_allocation_humongous(). Retrying the GC, in this case, 120 // will cause the requesting thread to spin inside collect() until the 121 // just started marking cycle is complete - which may be a while. So 122 // we do NOT retry the GC. 123 if (!res) { 124 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating"); 125 if (_gc_cause != GCCause::_g1_humongous_allocation) { 126 _should_retry_gc = true; 127 } 128 return; 129 } 130 } 131 132 // Try a partial collection of some kind. 133 _pause_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms); 134 135 if (_pause_succeeded) { 136 if (_word_size > 0) { 137 // An allocation had been requested. Do it, eventually trying a stronger 138 // kind of GC. 139 _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded); 140 } else { 141 bool should_upgrade_to_full = g1h->should_upgrade_to_full_gc(_gc_cause); 142 143 if (should_upgrade_to_full) { 144 // There has been a request to perform a GC to free some space. We have no 145 // information on how much memory has been asked for. In case there are 146 // absolutely no regions left to allocate into, do a maximally compacting full GC. 147 log_info(gc, ergo)("Attempting maximally compacting collection"); 148 _pause_succeeded = g1h->do_full_collection(false, /* explicit gc */ 149 true /* clear_all_soft_refs */); 150 } 151 } 152 guarantee(_pause_succeeded, "Elevated collections during the safepoint must always succeed."); 153 } else { 154 assert(_result == NULL, "invariant"); 155 // The only reason for the pause to not be successful is that, the GC locker is 156 // active (or has become active since the prologue was executed). In this case 157 // we should retry the pause after waiting for the GC locker to become inactive. 158 _should_retry_gc = true; 159 } 160 } 161 162 void VM_G1CollectForAllocation::doit_epilogue() { 163 VM_CollectForAllocation::doit_epilogue(); 164 165 // If the pause was initiated by a System.gc() and 166 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle 167 // that just started (or maybe one that was already in progress) to 168 // finish. 169 if (GCCause::is_user_requested_gc(_gc_cause) && 170 _should_initiate_conc_mark) { 171 assert(ExplicitGCInvokesConcurrent, 172 "the only way to be here is if ExplicitGCInvokesConcurrent is set"); 173 174 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 175 176 // In the doit() method we saved g1h->old_marking_cycles_completed() 177 // in the _old_marking_cycles_completed_before field. We have to 178 // wait until we observe that g1h->old_marking_cycles_completed() 179 // has increased by at least one. This can happen if a) we started 180 // a cycle and it completes, b) a cycle already in progress 181 // completes, or c) a Full GC happens. 182 183 // If the condition has already been reached, there's no point in 184 // actually taking the lock and doing the wait. 185 if (g1h->old_marking_cycles_completed() <= 186 _old_marking_cycles_completed_before) { 187 // The following is largely copied from CMS 188 189 Thread* thr = Thread::current(); 190 assert(thr->is_Java_thread(), "invariant"); 191 JavaThread* jt = (JavaThread*)thr; 192 ThreadToNativeFromVM native(jt); 193 194 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 195 while (g1h->old_marking_cycles_completed() <= 196 _old_marking_cycles_completed_before) { 197 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 198 } 199 } 200 } 201 } 202 203 void VM_G1Concurrent::doit() { 204 GCIdMark gc_id_mark(_gc_id); 205 GCTraceCPUTime tcpu; 206 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 207 GCTraceTime(Info, gc) t(_message, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true); 208 TraceCollectorStats tcs(g1h->g1mm()->conc_collection_counters()); 209 SvcGCMarker sgcm(SvcGCMarker::CONCURRENT); 210 IsGCActiveMark x; 211 _cl->do_void(); 212 } 213 214 bool VM_G1Concurrent::doit_prologue() { 215 Heap_lock->lock(); 216 return true; 217 } 218 219 void VM_G1Concurrent::doit_epilogue() { 220 if (Universe::has_reference_pending_list()) { 221 Heap_lock->notify_all(); 222 } 223 Heap_lock->unlock(); 224 }