Trace.h revision b194ec926bf3fb3c546244b135f602ceb3a0a6b0 
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_VIDEO            (1<<9)
54#define ATRACE_TAG_LAST             ATRACE_TAG_VIDEO
55
56#define ATRACE_TAG_VALID_MASK ((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST)
57
58#ifndef ATRACE_TAG
59#define ATRACE_TAG ATRACE_TAG_NEVER
60#elif ATRACE_TAG > ATRACE_TAG_LAST
61#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
62#endif
63
64// ATRACE_CALL traces the beginning and end of the current function.  To trace
65// the correct start and end times this macro should be the first line of the
66// function body.
67#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
68
69// ATRACE_INT traces a named integer value.  This can be used to track how the
70// value changes over time in a trace.
71#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
72
73// ATRACE_ENABLED returns true if the trace tag is enabled.  It can be used as a
74// guard condition around more expensive trace calculations.
75#define ATRACE_ENABLED() android::Tracer::isTagEnabled(ATRACE_TAG)
76
77namespace android {
78
79class Tracer {
80
81public:
82
83    static uint64_t getEnabledTags() {
84        initIfNeeded();
85        return sEnabledTags;
86    }
87
88    static inline bool isTagEnabled(uint64_t tag) {
89        initIfNeeded();
90        return sEnabledTags & tag;
91    }
92
93    static inline void traceCounter(uint64_t tag, const char* name,
94            int32_t value) {
95        if (CC_UNLIKELY(isTagEnabled(tag))) {
96            char buf[1024];
97            snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
98            write(sTraceFD, buf, strlen(buf));
99        }
100    }
101
102    static inline void traceBegin(uint64_t tag, const char* name) {
103        if (CC_UNLIKELY(isTagEnabled(tag))) {
104            char buf[1024];
105            size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
106            write(sTraceFD, buf, len);
107        }
108    }
109
110   static inline void traceEnd(uint64_t tag) {
111        if (CC_UNLIKELY(isTagEnabled(tag))) {
112            char buf = 'E';
113            write(sTraceFD, &buf, 1);
114        }
115    }
116
117private:
118
119    static inline void initIfNeeded() {
120        if (!android_atomic_acquire_load(&sIsReady)) {
121            init();
122        }
123    }
124
125    static void changeCallback();
126
127    // init opens the trace marker file for writing and reads the
128    // atrace.tags.enableflags system property.  It does this only the first
129    // time it is run, using sMutex for synchronization.
130    static void init();
131
132    // retrieve the current value of the system property.
133    static void loadSystemProperty();
134
135    // sIsReady is a boolean value indicating whether a call to init() has
136    // completed in this process.  It is initialized to 0 and set to 1 when the
137    // first init() call completes.  It is set to 1 even if a failure occurred
138    // in init (e.g. the trace marker file couldn't be opened).
139    //
140    // This should be checked by all tracing functions using an atomic acquire
141    // load operation before calling init().  This check avoids the need to lock
142    // a mutex each time a trace function gets called.
143    static volatile int32_t sIsReady;
144
145    // sTraceFD is the file descriptor used to write to the kernel's trace
146    // buffer.  It is initialized to -1 and set to an open file descriptor in
147    // init() while a lock on sMutex is held.
148    //
149    // This should only be used by a trace function after init() has
150    // successfully completed.
151    static int sTraceFD;
152
153    // sEnabledTags is the set of tag bits for which tracing is currently
154    // enabled.  It is initialized to 0 and set based on the
155    // atrace.tags.enableflags system property in init() while a lock on sMutex
156    // is held.
157    //
158    // This should only be used by a trace function after init() has
159    // successfully completed.
160    //
161    // This value is only ever non-zero when tracing is initialized and sTraceFD is not -1.
162    static uint64_t sEnabledTags;
163
164    // sMutex is used to protect the execution of init().
165    static Mutex sMutex;
166};
167
168class ScopedTrace {
169
170public:
171    inline ScopedTrace(uint64_t tag, const char* name) :
172            mTag(tag) {
173        Tracer::traceBegin(mTag, name);
174    }
175
176    inline ~ScopedTrace() {
177        Tracer::traceEnd(mTag);
178    }
179
180private:
181
182    uint64_t mTag;
183};
184
185}; // namespace android
186
187#endif // ANDROID_TRACE_H
188