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.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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24
25#ifndef SHARE_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP
26#define SHARE_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.
42class G1YoungRemSetSamplingThread: public ConcurrentGCThread {
43private:
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 check_for_periodic_gc();
54
55 void stop_service();
56
57 void sleep_before_next_cycle();
58
59 bool should_start_periodic_gc();
60
61public:
62 G1YoungRemSetSamplingThread();
63 double vtime_accum() { return _vtime_accum; }
64};
65
66#endif // SHARE_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP
67