1/*
2 * Copyright (C) 2012 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef StackStats_h
27#define StackStats_h
28
29#include "ExportMacros.h"
30#include <mutex>
31
32
33// Define this flag to enable Stack stats collection. This feature is useful
34// for getting a sample of native stack usage sizes.
35//
36// Enabling this will cause stats to be collected and written to a log file at
37// various  instrumented points in the code. It will result in noticeable
38// performance loss. Hence, this should only be enable when you want to do
39// some stats location in your local build. This code is provided here as a
40// convenience for collecting that data. It is not meant to be enabled by
41// default on release or debug builds.
42
43#define ENABLE_STACK_STATS 0
44
45
46namespace WTF {
47
48#if !ENABLE(STACK_STATS)
49
50class StackStats {
51public:
52    // The CheckPoint class is for marking check points corresponding
53    // each location in code where a stack recursion check is being done.
54
55    class CheckPoint {
56    public:
57        CheckPoint() { }
58    };
59
60    class PerThreadStats {
61    public:
62        PerThreadStats() { }
63    };
64
65    class LayoutCheckPoint {
66    public:
67        LayoutCheckPoint() { }
68    };
69
70    static void initialize() { }
71    static void probe() { }
72};
73
74#else // ENABLE(STACK_STATS)
75
76class StackStats {
77public:
78    // The CheckPoint class is for marking check points corresponding
79    // each location in code where a stack recursion check is being done.
80
81    class CheckPoint {
82    public:
83        CheckPoint();
84        ~CheckPoint();
85    private:
86        CheckPoint* m_prev;
87    };
88
89    class PerThreadStats {
90    public:
91        PerThreadStats();
92
93    private:
94        int m_reentryDepth;
95        char* m_stackStart;
96        CheckPoint* m_currentCheckPoint;
97
98        friend class CheckPoint;
99        friend class StackStats;
100    };
101
102    class LayoutCheckPoint {
103    public:
104        WTF_EXPORT_PRIVATE LayoutCheckPoint();
105        WTF_EXPORT_PRIVATE ~LayoutCheckPoint();
106
107    private:
108        LayoutCheckPoint* m_prev;
109        int m_depth;
110    };
111
112    // Initializes locks and the log file. Should only be called once.
113    static void initialize();
114
115    // Used for probing the stack at places where we suspect to be high
116    // points of stack usage but are NOT check points where stack recursion
117    // is checked.
118    //
119    // The more places where we add this probe, the more accurate our
120    // stats data will be. However, adding too many probes will also
121    // result in unnecessary performance loss. So, only add these probes
122    // judiciously where appropriate.
123    static void probe();
124
125private:
126    // CheckPoint management:
127    static std::mutex* s_sharedMutex;
128    static CheckPoint* s_topCheckPoint;
129    static LayoutCheckPoint* s_firstLayoutCheckPoint;
130    static LayoutCheckPoint* s_topLayoutCheckPoint;
131
132    // High watermark stats:
133    static int s_maxCheckPointDiff;
134    static int s_maxStackHeight;
135    static int s_maxReentryDepth;
136
137    static int s_maxLayoutCheckPointDiff;
138    static int s_maxTotalLayoutCheckPointDiff;
139    static int s_maxLayoutReentryDepth;
140
141    friend class CheckPoint;
142    friend class LayoutCheckPoint;
143};
144
145#endif // ENABLE(STACK_STATS)
146
147} // namespace WTF
148
149using WTF::StackStats;
150
151#endif // StackStats_h
152