Trace.h revision 555f89d8df316cdc5a25dbedb8614c2ac7a5e0a9 
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_WEBVIEW          (1<<4)
49#define ATRACE_TAG_WINDOW_MANAGER   (1<<5)
50#define ATRACE_TAG_ACTIVITY_MANAGER (1<<6)
51#define ATRACE_TAG_SYNC_MANAGER     (1<<7)
52#define ATRACE_TAG_AUDIO            (1<<8)
53#define ATRACE_TAG_LAST             ATRACE_TAG_AUDIO
54
55#define ATRACE_TAG_VALID_MASK ((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST)
56
57#ifndef ATRACE_TAG
58#define ATRACE_TAG ATRACE_TAG_NEVER
59#elif ATRACE_TAG > ATRACE_TAG_LAST
60#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
61#endif
62
63// ATRACE_CALL traces the beginning and end of the current function.  To trace
64// the correct start and end times this macro should be the first line of the
65// function body.
66#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
67
68// ATRACE_INT traces a named integer value.  This can be used to track how the
69// value changes over time in a trace.
70#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
71
72// ATRACE_ENABLED returns true if the trace tag is enabled.  It can be used as a
73// guard condition around more expensive trace calculations.
74#define ATRACE_ENABLED() android::Tracer::isTagEnabled(ATRACE_TAG)
75
76namespace android {
77
78class Tracer {
79
80public:
81
82    static uint64_t getEnabledTags() {
83        initIfNeeded();
84        return sEnabledTags;
85    }
86
87    static inline bool isTagEnabled(uint64_t tag) {
88        initIfNeeded();
89        return sEnabledTags & tag;
90    }
91
92    static inline void traceCounter(uint64_t tag, const char* name,
93            int32_t value) {
94        if (CC_UNLIKELY(isTagEnabled(tag))) {
95            char buf[1024];
96            snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
97            write(sTraceFD, buf, strlen(buf));
98        }
99    }
100
101    static inline void traceBegin(uint64_t tag, const char* name) {
102        if (CC_UNLIKELY(isTagEnabled(tag))) {
103            char buf[1024];
104            size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
105            write(sTraceFD, buf, len);
106        }
107    }
108
109   static inline void traceEnd(uint64_t tag) {
110        if (CC_UNLIKELY(isTagEnabled(tag))) {
111            char buf = 'E';
112            write(sTraceFD, &buf, 1);
113        }
114    }
115
116private:
117
118    static inline void initIfNeeded() {
119        if (!android_atomic_acquire_load(&sIsReady)) {
120            init();
121        }
122    }
123
124    static void changeCallback();
125
126    // init opens the trace marker file for writing and reads the
127    // atrace.tags.enableflags system property.  It does this only the first
128    // time it is run, using sMutex for synchronization.
129    static void init();
130
131    // retrieve the current value of the system property.
132    static void loadSystemProperty();
133
134    // sIsReady is a boolean value indicating whether a call to init() has
135    // completed in this process.  It is initialized to 0 and set to 1 when the
136    // first init() call completes.  It is set to 1 even if a failure occurred
137    // in init (e.g. the trace marker file couldn't be opened).
138    //
139    // This should be checked by all tracing functions using an atomic acquire
140    // load operation before calling init().  This check avoids the need to lock
141    // a mutex each time a trace function gets called.
142    static volatile int32_t sIsReady;
143
144    // sTraceFD is the file descriptor used to write to the kernel's trace
145    // buffer.  It is initialized to -1 and set to an open file descriptor in
146    // init() while a lock on sMutex is held.
147    //
148    // This should only be used by a trace function after init() has
149    // successfully completed.
150    static int sTraceFD;
151
152    // sEnabledTags is the set of tag bits for which tracing is currently
153    // enabled.  It is initialized to 0 and set based on the
154    // atrace.tags.enableflags system property in init() while a lock on sMutex
155    // is held.
156    //
157    // This should only be used by a trace function after init() has
158    // successfully completed.
159    //
160    // This value is only ever non-zero when tracing is initialized and sTraceFD is not -1.
161    static uint64_t sEnabledTags;
162
163    // sMutex is used to protect the execution of init().
164    static Mutex sMutex;
165};
166
167class ScopedTrace {
168
169public:
170    inline ScopedTrace(uint64_t tag, const char* name) :
171            mTag(tag) {
172        Tracer::traceBegin(mTag, name);
173    }
174
175    inline ~ScopedTrace() {
176        Tracer::traceEnd(mTag);
177    }
178
179private:
180
181    uint64_t mTag;
182};
183
184}; // namespace android
185
186#endif // ANDROID_TRACE_H
187