Trace.h revision 45b80c69ad8057fde0c0a76f7da3a2183a2aab96 
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//
42// These tags must be kept in sync with frameworks/base/core/java/android/os/Trace.java.
43#define ATRACE_TAG_NEVER    0           // The "never" tag is never enabled.
44#define ATRACE_TAG_ALWAYS   (1<<0)      // The "always" tag is always enabled.
45#define ATRACE_TAG_GRAPHICS (1<<1)
46#define ATRACE_TAG_INPUT    (1<<2)
47#define ATRACE_TAG_VIEW     (1<<3)
48#define ATRACE_TAG_LAST     ATRACE_TAG_VIEW
49
50#define ATRACE_TAG_VALID_MASK ((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST)
51
52#ifndef ATRACE_TAG
53#define ATRACE_TAG ATRACE_TAG_NEVER
54#elif ATRACE_TAG > ATRACE_TAG_LAST
55#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
56#endif
57
58// ATRACE_CALL traces the beginning and end of the current function.  To trace
59// the correct start and end times this macro should be the first line of the
60// function body.
61#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
62
63// ATRACE_INT traces a named integer value.  This can be used to track how the
64// value changes over time in a trace.
65#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
66
67// ATRACE_ENABLED returns true if the trace tag is enabled.  It can be used as a
68// guard condition around more expensive trace calculations.
69#define ATRACE_ENABLED() android::Tracer::isTagEnabled(ATRACE_TAG)
70
71namespace android {
72
73class Tracer {
74
75public:
76
77    static uint64_t getEnabledTags() {
78        initIfNeeded();
79        return sEnabledTags;
80    }
81
82    static inline bool isTagEnabled(uint64_t tag) {
83        initIfNeeded();
84        return sEnabledTags & tag;
85    }
86
87    static inline void traceCounter(uint64_t tag, const char* name,
88            int32_t value) {
89        if (CC_UNLIKELY(isTagEnabled(tag))) {
90            char buf[1024];
91            snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
92            write(sTraceFD, buf, strlen(buf));
93        }
94    }
95
96    static inline void traceBegin(uint64_t tag, const char* name) {
97        if (CC_UNLIKELY(isTagEnabled(tag))) {
98            char buf[1024];
99            size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
100            write(sTraceFD, buf, len);
101        }
102    }
103
104   static inline void traceEnd(uint64_t tag) {
105        if (CC_UNLIKELY(isTagEnabled(tag))) {
106            char buf = 'E';
107            write(sTraceFD, &buf, 1);
108        }
109    }
110
111private:
112
113    static inline void initIfNeeded() {
114        if (!android_atomic_acquire_load(&sIsReady)) {
115            init();
116        }
117    }
118
119    // init opens the trace marker file for writing and reads the
120    // atrace.tags.enableflags system property.  It does this only the first
121    // time it is run, using sMutex for synchronization.
122    static void init();
123
124    // sIsReady is a boolean value indicating whether a call to init() has
125    // completed in this process.  It is initialized to 0 and set to 1 when the
126    // first init() call completes.  It is set to 1 even if a failure occurred
127    // in init (e.g. the trace marker file couldn't be opened).
128    //
129    // This should be checked by all tracing functions using an atomic acquire
130    // load operation before calling init().  This check avoids the need to lock
131    // a mutex each time a trace function gets called.
132    static volatile int32_t sIsReady;
133
134    // sTraceFD is the file descriptor used to write to the kernel's trace
135    // buffer.  It is initialized to -1 and set to an open file descriptor in
136    // init() while a lock on sMutex is held.
137    //
138    // This should only be used by a trace function after init() has
139    // successfully completed.
140    static int sTraceFD;
141
142    // sEnabledTags is the set of tag bits for which tracing is currently
143    // enabled.  It is initialized to 0 and set based on the
144    // atrace.tags.enableflags system property in init() while a lock on sMutex
145    // is held.
146    //
147    // This should only be used by a trace function after init() has
148    // successfully completed.
149    //
150    // This value is only ever non-zero when tracing is initialized and sTraceFD is not -1.
151    static uint64_t sEnabledTags;
152
153    // sMutex is used to protect the execution of init().
154    static Mutex sMutex;
155};
156
157class ScopedTrace {
158
159public:
160    inline ScopedTrace(uint64_t tag, const char* name) :
161            mTag(tag) {
162        Tracer::traceBegin(mTag, name);
163    }
164
165    inline ~ScopedTrace() {
166        Tracer::traceEnd(mTag);
167    }
168
169private:
170
171    uint64_t mTag;
172};
173
174}; // namespace android
175
176#endif // ANDROID_TRACE_H
177