1/*
2 * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2018, Google and/or its affiliates. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26#ifndef SHARE_RUNTIME_THREADHEAPSAMPLER_HPP
27#define SHARE_RUNTIME_THREADHEAPSAMPLER_HPP
28
29#include "memory/allocation.hpp"
30
31class ThreadHeapSampler {
32 private:
33 // Statics for the fast log
34 static const int FastLogNumBits = 10;
35 static const int FastLogMask = (1 << FastLogNumBits) - 1;
36
37 size_t _bytes_until_sample;
38 // Cheap random number generator
39 static uint64_t _rnd;
40 static bool _log_table_initialized;
41
42 static double _log_table[1<<FastLogNumBits]; // Constant
43 static volatile int _sampling_interval;
44
45 void pick_next_geometric_sample();
46 void pick_next_sample(size_t overflowed_bytes = 0);
47
48 static double fast_log2(const double& d);
49 static bool init_log_table();
50 uint64_t next_random(uint64_t rnd);
51
52 public:
53 ThreadHeapSampler() : _bytes_until_sample(0) {
54 _rnd = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(this));
55 if (_rnd == 0) {
56 _rnd = 1;
57 }
58 }
59
60 size_t bytes_until_sample() { return _bytes_until_sample; }
61 void set_bytes_until_sample(size_t bytes) { _bytes_until_sample = bytes; }
62
63 void check_for_sampling(oop obj, size_t size_in_bytes, size_t bytes_allocated_before);
64
65 static void set_sampling_interval(int sampling_interval);
66 static int get_sampling_interval();
67};
68
69#endif // SHARE_RUNTIME_THREADHEAPSAMPLER_HPP
70