Trace.h revision f64b1ca000e0a5bb176f4e53f568e48dd1ecc71a 
1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_TRACE_H
18#define ANDROID_TRACE_H
19
20#include <fcntl.h>
21#include <stdint.h>
22#include <stdio.h>
23#include <string.h>
24#include <sys/stat.h>
25#include <sys/types.h>
26#include <unistd.h>
27
28#include <cutils/compiler.h>
29#include <utils/threads.h>
30
31// The ATRACE_TAG macro can be defined before including this header to trace
32// using one of the tags defined below.  It must be defined to one of the
33// following ATRACE_TAG_* macros.  The trace tag is used to filter tracing in
34// userland to avoid some of the runtime cost of tracing when it is not desired.
35//
36// Defining ATRACE_TAG to be ATRACE_TAG_ALWAYS will result in the tracing always
37// being enabled - this should ONLY be done for debug code, as userland tracing
38// has a performance cost even when the trace is not being recorded.  Defining
39// ATRACE_TAG to be ATRACE_TAG_NEVER or leaving ATRACE_TAG undefined will result
40// in the tracing always being disabled.
41#define ATRACE_TAG_NEVER    0           // The "never" tag is never enabled.
42#define ATRACE_TAG_ALWAYS   (1<<0)      // The "always" tag is always enabled.
43#define ATRACE_TAG_GRAPHICS (1<<1)
44#define ATRACE_TAG_LAST     (1<<1)
45
46#define ATRACE_TAG_INVALID (~((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST))
47
48#ifndef ATRACE_TAG
49#define ATRACE_TAG ATRACE_TAG_NEVER
50#elif ATRACE_TAG > ATRACE_TAG_LAST
51#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
52#endif
53
54// ATRACE_CALL traces the beginning and end of the current function.  To trace
55// the correct start and end times this macro should be the first line of the
56// function body.
57#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
58
59// ATRACE_INT traces a named integer value.  This can be used to track how the
60// value changes over time in a trace.
61#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
62
63namespace android {
64
65class Tracer {
66
67public:
68
69    static inline void traceCounter(uint64_t tag, const char* name,
70            int32_t value) {
71        if (!android_atomic_acquire_load(&sIsReady)) {
72            init();
73        }
74        int traceFD = sTraceFD;
75        if (CC_UNLIKELY(tagEnabled(tag) && traceFD != -1)) {
76            char buf[1024];
77            snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
78            write(traceFD, buf, strlen(buf));
79        }
80    }
81
82    static inline void traceBegin(uint64_t tag, const char* name) {
83        if (CC_UNLIKELY(!android_atomic_acquire_load(&sIsReady))) {
84            init();
85        }
86        int traceFD = sTraceFD;
87        if (CC_UNLIKELY(tagEnabled(tag) && (traceFD != -1))) {
88            char buf[1024];
89            size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
90            write(traceFD, buf, len);
91        }
92    }
93
94   static inline void traceEnd(uint64_t tag) {
95        if (CC_UNLIKELY(!android_atomic_acquire_load(&sIsReady))) {
96            init();
97        }
98        int traceFD = sTraceFD;
99        if (CC_UNLIKELY(tagEnabled(tag) && (traceFD != -1))) {
100            char buf = 'E';
101            write(traceFD, &buf, 1);
102        }
103    }
104
105private:
106
107    static inline bool tagEnabled(uint64_t tag) {
108        return !(tag & ATRACE_TAG_INVALID) && (tag & sEnabledTags);
109    }
110
111    // init opens the trace marker file for writing and reads the
112    // atrace.tags.enableflags system property.  It does this only the first
113    // time it is run, using sMutex for synchronization.
114    static void init();
115
116    // sIsReady is a boolean value indicating whether a call to init() has
117    // completed in this process.  It is initialized to 0 and set to 1 when the
118    // first init() call completes.  It is set to 1 even if a failure occurred
119    // in init (e.g. the trace marker file couldn't be opened).
120    //
121    // This should be checked by all tracing functions using an atomic acquire
122    // load operation before calling init().  This check avoids the need to lock
123    // a mutex each time a trace function gets called.
124    static volatile int32_t sIsReady;
125
126    // sTraceFD is the file descriptor used to write to the kernel's trace
127    // buffer.  It is initialized to -1 and set to an open file descriptor in
128    // init() while a lock on sMutex is held.
129    //
130    // This should only be used by a trace function after init() has
131    // successfully completed.
132    static int sTraceFD;
133
134    // sEnabledTags is the set of tag bits for which tracing is currently
135    // enabled.  It is initialized to 0 and set based on the
136    // atrace.tags.enableflags system property in init() while a lock on sMutex
137    // is held.
138    //
139    // This should only be used by a trace function after init() has
140    // successfully completed.
141    static uint64_t sEnabledTags;
142
143    // sMutex is used to protect the execution of init().
144    static Mutex sMutex;
145};
146
147class ScopedTrace {
148
149public:
150    inline ScopedTrace(uint64_t tag, const char* name) :
151            mTag(tag) {
152        Tracer::traceBegin(mTag, name);
153    }
154
155    inline ~ScopedTrace() {
156        Tracer::traceEnd(mTag);
157    }
158
159private:
160
161    uint64_t mTag;
162};
163
164}; // namespace android
165
166#endif // ANDROID_TRACE_H
167