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 #ifndef SHARE_VM_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP 26 #define SHARE_VM_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP 27 28 #include "gc/shared/concurrentGCThread.hpp" 29 30 // The G1YoungRemSetSamplingThread is used to re-assess the validity of 31 // the prediction for the remembered set lengths of the young generation. 32 // 33 // At the end of the GC G1 determines the length of the young gen based on 34 // how much time the next GC can take, and when the next GC may occur 35 // according to the MMU. 36 // 37 // The assumption is that a significant part of the GC is spent on scanning 38 // the remembered sets (and many other components), so this thread constantly 39 // reevaluates the prediction for the remembered set scanning costs, and potentially 40 // G1Policy resizes the young gen. This may do a premature GC or even 41 // increase the young gen size to keep pause time length goal. 42 class G1YoungRemSetSamplingThread: public ConcurrentGCThread { 43 private: 44 Monitor _monitor; 45 46 double _last_periodic_gc_attempt_s; 47 48 double _vtime_accum; // Accumulated virtual time. 49 50 void sample_young_list_rs_lengths(); 51 52 void run_service(); 53 void stop_service(); 54 55 void sleep_before_next_cycle(); 56 57 bool should_start_periodic_gc(); 58 59 public: 60 G1YoungRemSetSamplingThread(); 61 double vtime_accum() { return _vtime_accum; } 62 }; 63 64 #endif // SHARE_VM_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP