Trace.h revision 6acafadea0ef48acff794d12f5a64a81bcd7ef7c 
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_LAST     ATRACE_TAG_WEBVIEW
50
51#define ATRACE_TAG_VALID_MASK ((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST)
52
53#ifndef ATRACE_TAG
54#define ATRACE_TAG ATRACE_TAG_NEVER
55#elif ATRACE_TAG > ATRACE_TAG_LAST
56#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
57#endif
58
59// ATRACE_CALL traces the beginning and end of the current function.  To trace
60// the correct start and end times this macro should be the first line of the
61// function body.
62#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
63
64// ATRACE_INT traces a named integer value.  This can be used to track how the
65// value changes over time in a trace.
66#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
67
68// ATRACE_ENABLED returns true if the trace tag is enabled.  It can be used as a
69// guard condition around more expensive trace calculations.
70#define ATRACE_ENABLED() android::Tracer::isTagEnabled(ATRACE_TAG)
71
72namespace android {
73
74class Tracer {
75
76public:
77
78    static uint64_t getEnabledTags() {
79        initIfNeeded();
80        return sEnabledTags;
81    }
82
83    static inline bool isTagEnabled(uint64_t tag) {
84        initIfNeeded();
85        return sEnabledTags & tag;
86    }
87
88    static inline void traceCounter(uint64_t tag, const char* name,
89            int32_t value) {
90        if (CC_UNLIKELY(isTagEnabled(tag))) {
91            char buf[1024];
92            snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
93            write(sTraceFD, buf, strlen(buf));
94        }
95    }
96
97    static inline void traceBegin(uint64_t tag, const char* name) {
98        if (CC_UNLIKELY(isTagEnabled(tag))) {
99            char buf[1024];
100            size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
101            write(sTraceFD, buf, len);
102        }
103    }
104
105   static inline void traceEnd(uint64_t tag) {
106        if (CC_UNLIKELY(isTagEnabled(tag))) {
107            char buf = 'E';
108            write(sTraceFD, &buf, 1);
109        }
110    }
111
112private:
113
114    static inline void initIfNeeded() {
115        if (!android_atomic_acquire_load(&sIsReady)) {
116            init();
117        }
118    }
119
120    // init opens the trace marker file for writing and reads the
121    // atrace.tags.enableflags system property.  It does this only the first
122    // time it is run, using sMutex for synchronization.
123    static void init();
124
125    // sIsReady is a boolean value indicating whether a call to init() has
126    // completed in this process.  It is initialized to 0 and set to 1 when the
127    // first init() call completes.  It is set to 1 even if a failure occurred
128    // in init (e.g. the trace marker file couldn't be opened).
129    //
130    // This should be checked by all tracing functions using an atomic acquire
131    // load operation before calling init().  This check avoids the need to lock
132    // a mutex each time a trace function gets called.
133    static volatile int32_t sIsReady;
134
135    // sTraceFD is the file descriptor used to write to the kernel's trace
136    // buffer.  It is initialized to -1 and set to an open file descriptor in
137    // init() while a lock on sMutex is held.
138    //
139    // This should only be used by a trace function after init() has
140    // successfully completed.
141    static int sTraceFD;
142
143    // sEnabledTags is the set of tag bits for which tracing is currently
144    // enabled.  It is initialized to 0 and set based on the
145    // atrace.tags.enableflags system property in init() while a lock on sMutex
146    // is held.
147    //
148    // This should only be used by a trace function after init() has
149    // successfully completed.
150    //
151    // This value is only ever non-zero when tracing is initialized and sTraceFD is not -1.
152    static uint64_t sEnabledTags;
153
154    // sMutex is used to protect the execution of init().
155    static Mutex sMutex;
156};
157
158class ScopedTrace {
159
160public:
161    inline ScopedTrace(uint64_t tag, const char* name) :
162            mTag(tag) {
163        Tracer::traceBegin(mTag, name);
164    }
165
166    inline ~ScopedTrace() {
167        Tracer::traceEnd(mTag);
168    }
169
170private:
171
172    uint64_t mTag;
173};
174
175}; // namespace android
176
177#endif // ANDROID_TRACE_H
178