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/g1CollectionSet.hpp"
28#include "gc/g1/g1Policy.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
35G1YoungRemSetSamplingThread::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
45void 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
53void 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
69void G1YoungRemSetSamplingThread::stop_service() {
70  MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
71  _monitor.notify();
72}
73
74class G1YoungRemSetSamplingClosure : public HeapRegionClosure {
75  SuspendibleThreadSetJoiner* _sts;
76  size_t _regions_visited;
77  size_t _sampled_rs_lengths;
78public:
79  G1YoungRemSetSamplingClosure(SuspendibleThreadSetJoiner* sts) :
80    HeapRegionClosure(), _sts(sts), _regions_visited(0), _sampled_rs_lengths(0) { }
81
82  virtual bool doHeapRegion(HeapRegion* r) {
83    size_t rs_length = r->rem_set()->occupied();
84    _sampled_rs_lengths += rs_length;
85
86    // Update the collection set policy information for this region
87    G1CollectedHeap::heap()->collection_set()->update_young_region_prediction(r, rs_length);
88
89    _regions_visited++;
90
91    if (_regions_visited == 10) {
92      if (_sts->should_yield()) {
93        _sts->yield();
94        // A gc may have occurred and our sampling data is stale and further
95        // traversal of the collection set is unsafe
96        return true;
97      }
98      _regions_visited = 0;
99    }
100    return false;
101  }
102
103  size_t sampled_rs_lengths() const { return _sampled_rs_lengths; }
104};
105
106void G1YoungRemSetSamplingThread::sample_young_list_rs_lengths() {
107  SuspendibleThreadSetJoiner sts;
108  G1CollectedHeap* g1h = G1CollectedHeap::heap();
109  G1Policy* g1p = g1h->g1_policy();
110
111  if (g1p->adaptive_young_list_length()) {
112    G1YoungRemSetSamplingClosure cl(&sts);
113
114    G1CollectionSet* g1cs = g1h->collection_set();
115    g1cs->iterate(&cl);
116
117    if (cl.complete()) {
118      g1p->revise_young_list_target_length_if_necessary(cl.sampled_rs_lengths());
119    }
120  }
121}
122