Trace.java revision 6ad0452e6301c0650f58f3991f7c523f6f279ddb
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 17package android.os; 18 19import android.util.Log; 20 21/** 22 * Writes trace events to the system trace buffer. These trace events can be 23 * collected and visualized using the Systrace tool. 24 * 25 * This tracing mechanism is independent of the method tracing mechanism 26 * offered by {@link Debug#startMethodTracing}. In particular, it enables 27 * tracing of events that occur across multiple processes. 28 */ 29public final class Trace { 30 /* 31 * Writes trace events to the kernel trace buffer. These trace events can be 32 * collected using the "atrace" program for offline analysis. 33 */ 34 35 private static final String TAG = "Trace"; 36 37 // These tags must be kept in sync with system/core/include/cutils/trace.h. 38 /** @hide */ 39 public static final long TRACE_TAG_NEVER = 0; 40 /** @hide */ 41 public static final long TRACE_TAG_ALWAYS = 1L << 0; 42 /** @hide */ 43 public static final long TRACE_TAG_GRAPHICS = 1L << 1; 44 /** @hide */ 45 public static final long TRACE_TAG_INPUT = 1L << 2; 46 /** @hide */ 47 public static final long TRACE_TAG_VIEW = 1L << 3; 48 /** @hide */ 49 public static final long TRACE_TAG_WEBVIEW = 1L << 4; 50 /** @hide */ 51 public static final long TRACE_TAG_WINDOW_MANAGER = 1L << 5; 52 /** @hide */ 53 public static final long TRACE_TAG_ACTIVITY_MANAGER = 1L << 6; 54 /** @hide */ 55 public static final long TRACE_TAG_SYNC_MANAGER = 1L << 7; 56 /** @hide */ 57 public static final long TRACE_TAG_AUDIO = 1L << 8; 58 /** @hide */ 59 public static final long TRACE_TAG_VIDEO = 1L << 9; 60 /** @hide */ 61 public static final long TRACE_TAG_CAMERA = 1L << 10; 62 /** @hide */ 63 public static final long TRACE_TAG_HAL = 1L << 11; 64 /** @hide */ 65 public static final long TRACE_TAG_APP = 1L << 12; 66 /** @hide */ 67 public static final long TRACE_TAG_RESOURCES = 1L << 13; 68 69 private static final long TRACE_TAG_NOT_READY = 1L << 63; 70 private static final int MAX_SECTION_NAME_LEN = 127; 71 72 // Must be volatile to avoid word tearing. 73 private static volatile long sEnabledTags = TRACE_TAG_NOT_READY; 74 75 private static native long nativeGetEnabledTags(); 76 private static native void nativeTraceCounter(long tag, String name, int value); 77 private static native void nativeTraceBegin(long tag, String name); 78 private static native void nativeTraceEnd(long tag); 79 private static native void nativeAsyncTraceBegin(long tag, String name, int cookie); 80 private static native void nativeAsyncTraceEnd(long tag, String name, int cookie); 81 private static native void nativeSetAppTracingAllowed(boolean allowed); 82 private static native void nativeSetTracingEnabled(boolean allowed); 83 84 static { 85 // We configure two separate change callbacks, one in Trace.cpp and one here. The 86 // native callback reads the tags from the system property, and this callback 87 // reads the value that the native code retrieved. It's essential that the native 88 // callback executes first. 89 // 90 // The system provides ordering through a priority level. Callbacks made through 91 // SystemProperties.addChangeCallback currently have a negative priority, while 92 // our native code is using a priority of zero. 93 SystemProperties.addChangeCallback(new Runnable() { 94 @Override public void run() { 95 cacheEnabledTags(); 96 } 97 }); 98 } 99 100 private Trace() { 101 } 102 103 /** 104 * Caches a copy of the enabled-tag bits. The "master" copy is held by the native code, 105 * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property. 106 * <p> 107 * If the native code hasn't yet read the property, we will cause it to do one-time 108 * initialization. We don't want to do this during class init, because this class is 109 * preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote 110 * doesn't see the system-property update broadcasts.) 111 * <p> 112 * We want to defer initialization until the first use by an app, post-zygote. 113 * <p> 114 * We're okay if multiple threads call here simultaneously -- the native state is 115 * synchronized, and sEnabledTags is volatile (prevents word tearing). 116 */ 117 private static long cacheEnabledTags() { 118 long tags = nativeGetEnabledTags(); 119 sEnabledTags = tags; 120 return tags; 121 } 122 123 /** 124 * Returns true if a trace tag is enabled. 125 * 126 * @param traceTag The trace tag to check. 127 * @return True if the trace tag is valid. 128 * 129 * @hide 130 */ 131 public static boolean isTagEnabled(long traceTag) { 132 long tags = sEnabledTags; 133 if (tags == TRACE_TAG_NOT_READY) { 134 tags = cacheEnabledTags(); 135 } 136 return (tags & traceTag) != 0; 137 } 138 139 /** 140 * Writes trace message to indicate the value of a given counter. 141 * 142 * @param traceTag The trace tag. 143 * @param counterName The counter name to appear in the trace. 144 * @param counterValue The counter value. 145 * 146 * @hide 147 */ 148 public static void traceCounter(long traceTag, String counterName, int counterValue) { 149 if (isTagEnabled(traceTag)) { 150 nativeTraceCounter(traceTag, counterName, counterValue); 151 } 152 } 153 154 /** 155 * Set whether application tracing is allowed for this process. This is intended to be set 156 * once at application start-up time based on whether the application is debuggable. 157 * 158 * @hide 159 */ 160 public static void setAppTracingAllowed(boolean allowed) { 161 nativeSetAppTracingAllowed(allowed); 162 163 // Setting whether app tracing is allowed may change the tags, so we update the cached 164 // tags here. 165 cacheEnabledTags(); 166 } 167 168 /** 169 * Set whether tracing is enabled in this process. Tracing is disabled shortly after Zygote 170 * initializes and re-enabled after processes fork from Zygote. This is done because Zygote 171 * has no way to be notified about changes to the tracing tags, and if Zygote ever reads and 172 * caches the tracing tags, forked processes will inherit those stale tags. 173 * 174 * @hide 175 */ 176 public static void setTracingEnabled(boolean enabled) { 177 nativeSetTracingEnabled(enabled); 178 179 // Setting whether tracing is enabled may change the tags, so we update the cached tags 180 // here. 181 cacheEnabledTags(); 182 } 183 184 /** 185 * Writes a trace message to indicate that a given section of code has 186 * begun. Must be followed by a call to {@link #traceEnd} using the same 187 * tag. 188 * 189 * @param traceTag The trace tag. 190 * @param methodName The method name to appear in the trace. 191 * 192 * @hide 193 */ 194 public static void traceBegin(long traceTag, String methodName) { 195 if (isTagEnabled(traceTag)) { 196 nativeTraceBegin(traceTag, methodName); 197 } 198 } 199 200 /** 201 * Writes a trace message to indicate that the current method has ended. 202 * Must be called exactly once for each call to {@link #traceBegin} using the same tag. 203 * 204 * @param traceTag The trace tag. 205 * 206 * @hide 207 */ 208 public static void traceEnd(long traceTag) { 209 if (isTagEnabled(traceTag)) { 210 nativeTraceEnd(traceTag); 211 } 212 } 213 214 /** 215 * Writes a trace message to indicate that a given section of code has 216 * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same 217 * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)}, 218 * asynchronous events do not need to be nested. The name and cookie used to 219 * begin an event must be used to end it. 220 * 221 * @param traceTag The trace tag. 222 * @param methodName The method name to appear in the trace. 223 * @param cookie Unique identifier for distinguishing simultaneous events 224 * 225 * @hide 226 */ 227 public static void asyncTraceBegin(long traceTag, String methodName, int cookie) { 228 if (isTagEnabled(traceTag)) { 229 nativeAsyncTraceBegin(traceTag, methodName, cookie); 230 } 231 } 232 233 /** 234 * Writes a trace message to indicate that the current method has ended. 235 * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)} 236 * using the same tag, name and cookie. 237 * 238 * @param traceTag The trace tag. 239 * @param methodName The method name to appear in the trace. 240 * @param cookie Unique identifier for distinguishing simultaneous events 241 * 242 * @hide 243 */ 244 public static void asyncTraceEnd(long traceTag, String methodName, int cookie) { 245 if (isTagEnabled(traceTag)) { 246 nativeAsyncTraceEnd(traceTag, methodName, cookie); 247 } 248 } 249 250 /** 251 * Writes a trace message to indicate that a given section of code has begun. This call must 252 * be followed by a corresponding call to {@link #endSection()} on the same thread. 253 * 254 * <p class="note"> At this time the vertical bar character '|', newline character '\n', and 255 * null character '\0' are used internally by the tracing mechanism. If sectionName contains 256 * these characters they will be replaced with a space character in the trace. 257 * 258 * @param sectionName The name of the code section to appear in the trace. This may be at 259 * most 127 Unicode code units long. 260 */ 261 public static void beginSection(String sectionName) { 262 if (isTagEnabled(TRACE_TAG_APP)) { 263 if (sectionName.length() > MAX_SECTION_NAME_LEN) { 264 throw new IllegalArgumentException("sectionName is too long"); 265 } 266 nativeTraceBegin(TRACE_TAG_APP, sectionName); 267 } 268 } 269 270 /** 271 * Writes a trace message to indicate that a given section of code has ended. This call must 272 * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method 273 * will mark the end of the most recently begun section of code, so care must be taken to 274 * ensure that beginSection / endSection pairs are properly nested and called from the same 275 * thread. 276 */ 277 public static void endSection() { 278 if (isTagEnabled(TRACE_TAG_APP)) { 279 nativeTraceEnd(TRACE_TAG_APP); 280 } 281 } 282} 283