Trace.h revision 1737e57a861326e96f3de19090975564f98a8fda 
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_CAMERA           (1<<10)
55#define ATRACE_TAG_LAST             ATRACE_TAG_CAMERA
56
57#define ATRACE_TAG_VALID_MASK ((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST)
58
59#ifndef ATRACE_TAG
60#define ATRACE_TAG ATRACE_TAG_NEVER
61#elif ATRACE_TAG > ATRACE_TAG_LAST
62#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
63#endif
64
65// ATRACE_CALL traces the beginning and end of the current function.  To trace
66// the correct start and end times this macro should be the first line of the
67// function body.
68#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
69
70// ATRACE_INT traces a named integer value.  This can be used to track how the
71// value changes over time in a trace.
72#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
73
74// ATRACE_ENABLED returns true if the trace tag is enabled.  It can be used as a
75// guard condition around more expensive trace calculations.
76#define ATRACE_ENABLED() android::Tracer::isTagEnabled(ATRACE_TAG)
77
78namespace android {
79
80class Tracer {
81
82public:
83
84    static uint64_t getEnabledTags() {
85        initIfNeeded();
86        return sEnabledTags;
87    }
88
89    static inline bool isTagEnabled(uint64_t tag) {
90        initIfNeeded();
91        return sEnabledTags & tag;
92    }
93
94    static inline void traceCounter(uint64_t tag, const char* name,
95            int32_t value) {
96        if (CC_UNLIKELY(isTagEnabled(tag))) {
97            char buf[1024];
98            snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
99            write(sTraceFD, buf, strlen(buf));
100        }
101    }
102
103    static inline void traceBegin(uint64_t tag, const char* name) {
104        if (CC_UNLIKELY(isTagEnabled(tag))) {
105            char buf[1024];
106            size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
107            write(sTraceFD, buf, len);
108        }
109    }
110
111   static inline void traceEnd(uint64_t tag) {
112        if (CC_UNLIKELY(isTagEnabled(tag))) {
113            char buf = 'E';
114            write(sTraceFD, &buf, 1);
115        }
116    }
117
118private:
119
120    static inline void initIfNeeded() {
121        if (!android_atomic_acquire_load(&sIsReady)) {
122            init();
123        }
124    }
125
126    static void changeCallback();
127
128    // init opens the trace marker file for writing and reads the
129    // atrace.tags.enableflags system property.  It does this only the first
130    // time it is run, using sMutex for synchronization.
131    static void init();
132
133    // retrieve the current value of the system property.
134    static void loadSystemProperty();
135
136    // sIsReady is a boolean value indicating whether a call to init() has
137    // completed in this process.  It is initialized to 0 and set to 1 when the
138    // first init() call completes.  It is set to 1 even if a failure occurred
139    // in init (e.g. the trace marker file couldn't be opened).
140    //
141    // This should be checked by all tracing functions using an atomic acquire
142    // load operation before calling init().  This check avoids the need to lock
143    // a mutex each time a trace function gets called.
144    static volatile int32_t sIsReady;
145
146    // sTraceFD is the file descriptor used to write to the kernel's trace
147    // buffer.  It is initialized to -1 and set to an open file descriptor in
148    // init() while a lock on sMutex is held.
149    //
150    // This should only be used by a trace function after init() has
151    // successfully completed.
152    static int sTraceFD;
153
154    // sEnabledTags is the set of tag bits for which tracing is currently
155    // enabled.  It is initialized to 0 and set based on the
156    // atrace.tags.enableflags system property in init() while a lock on sMutex
157    // is held.
158    //
159    // This should only be used by a trace function after init() has
160    // successfully completed.
161    //
162    // This value is only ever non-zero when tracing is initialized and sTraceFD is not -1.
163    static uint64_t sEnabledTags;
164
165    // sMutex is used to protect the execution of init().
166    static Mutex sMutex;
167};
168
169class ScopedTrace {
170
171public:
172    inline ScopedTrace(uint64_t tag, const char* name) :
173            mTag(tag) {
174        Tracer::traceBegin(mTag, name);
175    }
176
177    inline ~ScopedTrace() {
178        Tracer::traceEnd(mTag);
179    }
180
181private:
182
183    uint64_t mTag;
184};
185
186}; // namespace android
187
188#endif // ANDROID_TRACE_H
189