1 /* 2 * Copyright (c) 2001, 2018, 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/g1Policy.hpp" 29 #include "gc/shared/gcId.hpp" 30 #include "gc/g1/vm_operations_g1.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 g1h->do_full_collection(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 _target_pause_time_ms(target_pause_time_ms), 51 _should_retry_gc(false), 52 _old_marking_cycles_completed_before(0) { 53 guarantee(target_pause_time_ms > 0.0, 54 "target_pause_time_ms = %1.6lf should be positive", 55 target_pause_time_ms); 56 _gc_cause = gc_cause; 57 } 58 59 bool VM_G1CollectForAllocation::doit_prologue() { 60 bool res = VM_CollectForAllocation::doit_prologue(); 61 if (!res) { 62 if (_should_initiate_conc_mark) { 63 // The prologue can fail for a couple of reasons. The first is that another GC 64 // got scheduled and prevented the scheduling of the initial mark GC. The 65 // second is that the GC locker may be active and the heap can't be expanded. 66 // In both cases we want to retry the GC so that the initial mark pause is 67 // actually scheduled. In the second case, however, we should stall until 68 // until the GC locker is no longer active and then retry the initial mark GC. 69 _should_retry_gc = true; 70 } 71 } 72 return res; 73 } 74 75 void VM_G1CollectForAllocation::doit() { 76 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 77 assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause), 78 "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle"); 79 80 if (_word_size > 0) { 81 // An allocation has been requested. So, try to do that first. 82 _result = g1h->attempt_allocation_at_safepoint(_word_size, 83 false /* expect_null_cur_alloc_region */); 84 if (_result != NULL) { 85 // If we can successfully allocate before we actually do the 86 // pause then we will consider this pause successful. 87 _pause_succeeded = true; 88 return; 89 } 90 } 91 92 GCCauseSetter x(g1h, _gc_cause); 93 if (_should_initiate_conc_mark) { 94 // It's safer to read old_marking_cycles_completed() here, given 95 // that noone else will be updating it concurrently. Since we'll 96 // only need it if we're initiating a marking cycle, no point in 97 // setting it earlier. 98 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed(); 99 100 // At this point we are supposed to start a concurrent cycle. We 101 // will do so if one is not already in progress. 102 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause); 103 104 // The above routine returns true if we were able to force the 105 // next GC pause to be an initial mark; it returns false if a 106 // marking cycle is already in progress. 107 // 108 // If a marking cycle is already in progress just return and skip the 109 // pause below - if the reason for requesting this initial mark pause 110 // was due to a System.gc() then the requesting thread should block in 111 // doit_epilogue() until the marking cycle is complete. 112 // 113 // If this initial mark pause was requested as part of a humongous 114 // allocation then we know that the marking cycle must just have 115 // been started by another thread (possibly also allocating a humongous 116 // object) as there was no active marking cycle when the requesting 117 // thread checked before calling collect() in 118 // attempt_allocation_humongous(). Retrying the GC, in this case, 119 // will cause the requesting thread to spin inside collect() until the 120 // just started marking cycle is complete - which may be a while. So 121 // we do NOT retry the GC. 122 if (!res) { 123 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating"); 124 if (_gc_cause != GCCause::_g1_humongous_allocation) { 125 _should_retry_gc = true; 126 } 127 return; 128 } 129 } 130 131 // Try a partial collection of some kind. 132 _pause_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms); 133 134 if (_pause_succeeded) { 135 if (_word_size > 0) { 136 // An allocation had been requested. Do it, eventually trying a stronger 137 // kind of GC. 138 _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded); 139 } else { 140 bool should_upgrade_to_full = !g1h->should_do_concurrent_full_gc(_gc_cause) && 141 !g1h->has_regions_left_for_allocation(); 142 if (should_upgrade_to_full) { 143 // There has been a request to perform a GC to free some space. We have no 144 // information on how much memory has been asked for. In case there are 145 // absolutely no regions left to allocate into, do a maximally compacting full GC. 146 log_info(gc, ergo)("Attempting maximally compacting collection"); 147 _pause_succeeded = g1h->do_full_collection(false, /* explicit gc */ 148 true /* clear_all_soft_refs */); 149 } 150 } 151 guarantee(_pause_succeeded, "Elevated collections during the safepoint must always succeed."); 152 } else { 153 assert(_result == NULL, "invariant"); 154 // The only reason for the pause to not be successful is that, the GC locker is 155 // active (or has become active since the prologue was executed). In this case 156 // we should retry the pause after waiting for the GC locker to become inactive. 157 _should_retry_gc = true; 158 } 159 } 160 161 void VM_G1CollectForAllocation::doit_epilogue() { 162 VM_CollectForAllocation::doit_epilogue(); 163 164 // If the pause was initiated by a System.gc() and 165 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle 166 // that just started (or maybe one that was already in progress) to 167 // finish. 168 if (GCCause::is_user_requested_gc(_gc_cause) && 169 _should_initiate_conc_mark) { 170 assert(ExplicitGCInvokesConcurrent, 171 "the only way to be here is if ExplicitGCInvokesConcurrent is set"); 172 173 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 174 175 // In the doit() method we saved g1h->old_marking_cycles_completed() 176 // in the _old_marking_cycles_completed_before field. We have to 177 // wait until we observe that g1h->old_marking_cycles_completed() 178 // has increased by at least one. This can happen if a) we started 179 // a cycle and it completes, b) a cycle already in progress 180 // completes, or c) a Full GC happens. 181 182 // If the condition has already been reached, there's no point in 183 // actually taking the lock and doing the wait. 184 if (g1h->old_marking_cycles_completed() <= 185 _old_marking_cycles_completed_before) { 186 // The following is largely copied from CMS 187 188 Thread* thr = Thread::current(); 189 assert(thr->is_Java_thread(), "invariant"); 190 JavaThread* jt = (JavaThread*)thr; 191 ThreadToNativeFromVM native(jt); 192 193 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 194 while (g1h->old_marking_cycles_completed() <= 195 _old_marking_cycles_completed_before) { 196 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag); 197 } 198 } 199 } 200 } 201 202 void VM_CGC_Operation::doit() { 203 GCIdMark gc_id_mark(_gc_id); 204 GCTraceCPUTime tcpu; 205 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 206 GCTraceTime(Info, gc) t(_printGCMessage, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true); 207 TraceCollectorStats tcs(g1h->g1mm()->conc_collection_counters()); 208 SvcGCMarker sgcm(SvcGCMarker::CONCURRENT); 209 IsGCActiveMark x; 210 _cl->do_void(); 211 } 212 213 bool VM_CGC_Operation::doit_prologue() { 214 Heap_lock->lock(); 215 return true; 216 } 217 218 void VM_CGC_Operation::doit_epilogue() { 219 if (Universe::has_reference_pending_list()) { 220 Heap_lock->notify_all(); 221 } 222 Heap_lock->unlock(); 223 }