1 /* 2 * Copyright (c) 2015, 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/g1CollectionSet.hpp" 28 #include "gc/g1/g1ConcurrentMark.inline.hpp" 29 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 30 #include "gc/g1/g1Policy.hpp" 31 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 32 #include "gc/g1/heapRegion.inline.hpp" 33 #include "gc/g1/heapRegionRemSet.hpp" 34 #include "gc/shared/suspendibleThreadSet.hpp" 35 #include "runtime/mutexLocker.hpp" 36 37 G1YoungRemSetSamplingThread::G1YoungRemSetSamplingThread() : 38 ConcurrentGCThread(), 39 _monitor(Mutex::nonleaf, 40 "G1YoungRemSetSamplingThread monitor", 41 true, 42 Monitor::_safepoint_check_never), 43 _last_periodic_gc_attempt_s(os::elapsedTime()), 44 _vtime_accum(0) { 45 set_name("G1 Young RemSet Sampling"); 46 create_and_start(); 47 } 48 49 void G1YoungRemSetSamplingThread::sleep_before_next_cycle() { 50 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag); 51 if (!should_terminate()) { 52 uintx waitms = G1ConcRefinementServiceIntervalMillis; 53 _monitor.wait(Mutex::_no_safepoint_check_flag, waitms); 54 } 55 } 56 57 bool G1YoungRemSetSamplingThread::should_start_periodic_gc() { 58 // If we are currently in a concurrent mark we are going to uncommit memory soon. 59 if (G1CollectedHeap::heap()->concurrent_mark()->cm_thread()->during_cycle()) { 60 log_debug(gc, periodic)("Concurrent cycle in progress. Skipping."); 61 return false; 62 } 63 64 // Check if enough time has passed since the last GC. 65 uintx time_since_last_gc = (uintx)Universe::heap()->millis_since_last_gc(); 66 if ((time_since_last_gc < G1PeriodicGCInterval)) { 67 log_debug(gc, periodic)("Last GC occurred " UINTX_FORMAT "ms before which is below threshold " UINTX_FORMAT "ms. Skipping.", 68 time_since_last_gc, G1PeriodicGCInterval); 69 return false; 70 } 71 72 // Check if load is lower than max. 73 double recent_load; 74 if ((G1PeriodicGCSystemLoadThreshold > 0.0f) && 75 (os::loadavg(&recent_load, 1) == -1 || recent_load > G1PeriodicGCSystemLoadThreshold)) { 76 log_debug(gc, periodic)("Load %1.2f is higher than threshold %1.2f. Skipping.", 77 recent_load, G1PeriodicGCSystemLoadThreshold); 78 return false; 79 } 80 81 return true; 82 } 83 84 void G1YoungRemSetSamplingThread::check_for_periodic_gc(){ 85 // If disabled, just return. 86 if (G1PeriodicGCInterval == 0) { 87 return; 88 } 89 if ((os::elapsedTime() - _last_periodic_gc_attempt_s) > (G1PeriodicGCInterval / 1000.0)) { 90 log_debug(gc, periodic)("Checking for periodic GC."); 91 if (should_start_periodic_gc()) { 92 if (!G1CollectedHeap::heap()->attempt_collect(GCCause::_g1_periodic_collection, 93 false /* retry_on_vmop_failure */)) { 94 log_debug(gc, periodic)("GC request denied. Skipping."); 95 } 96 } 97 _last_periodic_gc_attempt_s = os::elapsedTime(); 98 } 99 } 100 101 void G1YoungRemSetSamplingThread::run_service() { 102 double vtime_start = os::elapsedVTime(); 103 104 // Print a message about periodic GC configuration. 105 if (G1PeriodicGCInterval != 0) { 106 log_info(gc)("Periodic GC enabled with interval " UINTX_FORMAT "ms", G1PeriodicGCInterval); 107 } else { 108 log_info(gc)("Periodic GC disabled"); 109 } 110 111 while (!should_terminate()) { 112 sample_young_list_rs_lengths(); 113 114 if (os::supports_vtime()) { 115 _vtime_accum = (os::elapsedVTime() - vtime_start); 116 } else { 117 _vtime_accum = 0.0; 118 } 119 120 check_for_periodic_gc(); 121 122 sleep_before_next_cycle(); 123 } 124 } 125 126 void G1YoungRemSetSamplingThread::stop_service() { 127 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag); 128 _monitor.notify(); 129 } 130 131 class G1YoungRemSetSamplingClosure : public HeapRegionClosure { 132 SuspendibleThreadSetJoiner* _sts; 133 size_t _regions_visited; 134 size_t _sampled_rs_lengths; 135 public: 136 G1YoungRemSetSamplingClosure(SuspendibleThreadSetJoiner* sts) : 137 HeapRegionClosure(), _sts(sts), _regions_visited(0), _sampled_rs_lengths(0) { } 138 139 virtual bool do_heap_region(HeapRegion* r) { 140 size_t rs_length = r->rem_set()->occupied(); 141 _sampled_rs_lengths += rs_length; 142 143 // Update the collection set policy information for this region 144 G1CollectedHeap::heap()->collection_set()->update_young_region_prediction(r, rs_length); 145 146 _regions_visited++; 147 148 if (_regions_visited == 10) { 149 if (_sts->should_yield()) { 150 _sts->yield(); 151 // A gc may have occurred and our sampling data is stale and further 152 // traversal of the collection set is unsafe 153 return true; 154 } 155 _regions_visited = 0; 156 } 157 return false; 158 } 159 160 size_t sampled_rs_lengths() const { return _sampled_rs_lengths; } 161 }; 162 163 void G1YoungRemSetSamplingThread::sample_young_list_rs_lengths() { 164 SuspendibleThreadSetJoiner sts; 165 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 166 G1Policy* g1p = g1h->policy(); 167 168 if (g1p->adaptive_young_list_length()) { 169 G1YoungRemSetSamplingClosure cl(&sts); 170 171 G1CollectionSet* g1cs = g1h->collection_set(); 172 g1cs->iterate(&cl); 173 174 if (cl.is_complete()) { 175 g1p->revise_young_list_target_length_if_necessary(cl.sampled_rs_lengths()); 176 } 177 } 178 }