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