1 /* 2 * Copyright (c) 2015, 2016, 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/g1CollectorPolicy.hpp" 28 #include "gc/g1/g1CollectionSet.hpp" 29 #include "gc/g1/g1YoungRemSetSamplingThread.hpp" 30 #include "gc/g1/heapRegion.inline.hpp" 31 #include "gc/g1/heapRegionRemSet.hpp" 32 #include "gc/g1/suspendibleThreadSet.hpp" 33 #include "runtime/mutexLocker.hpp" 34 35 G1YoungRemSetSamplingThread::G1YoungRemSetSamplingThread() : 36 ConcurrentGCThread(), 37 _monitor(Mutex::nonleaf, 38 "G1YoungRemSetSamplingThread monitor", 39 true, 40 Monitor::_safepoint_check_never) { 41 set_name("G1 Young RemSet Sampling"); 42 create_and_start(); 43 } 44 45 void G1YoungRemSetSamplingThread::sleep_before_next_cycle() { 46 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag); 47 if (!should_terminate()) { 48 uintx waitms = G1ConcRefinementServiceIntervalMillis; // 300, really should be? 49 _monitor.wait(Mutex::_no_safepoint_check_flag, waitms); 50 } 51 } 52 53 void G1YoungRemSetSamplingThread::run_service() { 54 double vtime_start = os::elapsedVTime(); 55 56 while (!should_terminate()) { 57 sample_young_list_rs_lengths(); 58 59 if (os::supports_vtime()) { 60 _vtime_accum = (os::elapsedVTime() - vtime_start); 61 } else { 62 _vtime_accum = 0.0; 63 } 64 65 sleep_before_next_cycle(); 66 } 67 } 68 69 void G1YoungRemSetSamplingThread::stop_service() { 70 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag); 71 _monitor.notify(); 72 } 73 74 void G1YoungRemSetSamplingThread::sample_young_list_rs_lengths() { 75 SuspendibleThreadSetJoiner sts; 76 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 77 G1CollectorPolicy* g1p = g1h->g1_policy(); 78 if (g1p->adaptive_young_list_length()) { 79 int regions_visited = 0; 80 HeapRegion* hr = g1h->young_list()->first_region(); 81 size_t sampled_rs_lengths = 0; 82 83 while (hr != NULL) { 84 size_t rs_length = hr->rem_set()->occupied(); 85 sampled_rs_lengths += rs_length; 86 87 // The current region may not yet have been added to the 88 // incremental collection set (it gets added when it is 89 // retired as the current allocation region). 90 if (hr->in_collection_set()) { 91 // Update the collection set policy information for this region 92 g1h->collection_set()->update_young_region_prediction(hr, rs_length); 93 } 94 95 ++regions_visited; 96 97 // we try to yield every time we visit 10 regions 98 if (regions_visited == 10) { 99 if (sts.should_yield()) { 100 sts.yield(); 101 // A gc may have occurred and our sampling data is stale and further 102 // traversal of the young list is unsafe 103 return; 104 } 105 regions_visited = 0; 106 } 107 hr = hr->get_next_young_region(); 108 } 109 g1p->revise_young_list_target_length_if_necessary(sampled_rs_lengths); 110 } 111 }