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 package android.os; 18 19 /** 20 * Writes trace events to the system trace buffer. These trace events can be 21 * collected and visualized using the Systrace tool. 22 * 23 * <p>This tracing mechanism is independent of the method tracing mechanism 24 * offered by {@link Debug#startMethodTracing}. In particular, it enables 25 * tracing of events that occur across multiple processes. 26 * <p>For information about using the Systrace tool, read <a 27 * href="{@docRoot}tools/debugging/systrace.html">Analyzing Display and Performance 28 * with Systrace</a>. 29 */ 30 public final class Trace { 31 /* 32 * Writes trace events to the kernel trace buffer. These trace events can be 33 * collected using the "atrace" program for offline analysis. 34 */ 35 36 private static final String TAG = "Trace"; 37 38 // These tags must be kept in sync with system/core/include/cutils/trace.h. 39 // They should also be added to frameworks/native/cmds/atrace/atrace.cpp. 40 /** @hide */ 41 public static final long TRACE_TAG_NEVER = 0; 42 /** @hide */ 43 public static final long TRACE_TAG_ALWAYS = 1L << 0; 44 /** @hide */ 45 public static final long TRACE_TAG_GRAPHICS = 1L << 1; 46 /** @hide */ 47 public static final long TRACE_TAG_INPUT = 1L << 2; 48 /** @hide */ 49 public static final long TRACE_TAG_VIEW = 1L << 3; 50 /** @hide */ 51 public static final long TRACE_TAG_WEBVIEW = 1L << 4; 52 /** @hide */ 53 public static final long TRACE_TAG_WINDOW_MANAGER = 1L << 5; 54 /** @hide */ 55 public static final long TRACE_TAG_ACTIVITY_MANAGER = 1L << 6; 56 /** @hide */ 57 public static final long TRACE_TAG_SYNC_MANAGER = 1L << 7; 58 /** @hide */ 59 public static final long TRACE_TAG_AUDIO = 1L << 8; 60 /** @hide */ 61 public static final long TRACE_TAG_VIDEO = 1L << 9; 62 /** @hide */ 63 public static final long TRACE_TAG_CAMERA = 1L << 10; 64 /** @hide */ 65 public static final long TRACE_TAG_HAL = 1L << 11; 66 /** @hide */ 67 public static final long TRACE_TAG_APP = 1L << 12; 68 /** @hide */ 69 public static final long TRACE_TAG_RESOURCES = 1L << 13; 70 /** @hide */ 71 public static final long TRACE_TAG_DALVIK = 1L << 14; 72 /** @hide */ 73 public static final long TRACE_TAG_RS = 1L << 15; 74 /** @hide */ 75 public static final long TRACE_TAG_BIONIC = 1L << 16; 76 /** @hide */ 77 public static final long TRACE_TAG_POWER = 1L << 17; 78 /** @hide */ 79 public static final long TRACE_TAG_PACKAGE_MANAGER = 1L << 18; 80 /** @hide */ 81 public static final long TRACE_TAG_SYSTEM_SERVER = 1L << 19; 82 /** @hide */ 83 public static final long TRACE_TAG_DATABASE = 1L << 20; 84 /** @hide */ 85 public static final long TRACE_TAG_NETWORK = 1L << 21; 86 87 private static final long TRACE_TAG_NOT_READY = 1L << 63; 88 private static final int MAX_SECTION_NAME_LEN = 127; 89 90 // Must be volatile to avoid word tearing. 91 private static volatile long sEnabledTags = TRACE_TAG_NOT_READY; 92 93 private static native long nativeGetEnabledTags(); 94 private static native void nativeTraceCounter(long tag, String name, int value); 95 private static native void nativeTraceBegin(long tag, String name); 96 private static native void nativeTraceEnd(long tag); 97 private static native void nativeAsyncTraceBegin(long tag, String name, int cookie); 98 private static native void nativeAsyncTraceEnd(long tag, String name, int cookie); 99 private static native void nativeSetAppTracingAllowed(boolean allowed); 100 private static native void nativeSetTracingEnabled(boolean allowed); 101 102 static { 103 // We configure two separate change callbacks, one in Trace.cpp and one here. The 104 // native callback reads the tags from the system property, and this callback 105 // reads the value that the native code retrieved. It's essential that the native 106 // callback executes first. 107 // 108 // The system provides ordering through a priority level. Callbacks made through 109 // SystemProperties.addChangeCallback currently have a negative priority, while 110 // our native code is using a priority of zero. 111 SystemProperties.addChangeCallback(new Runnable() { 112 @Override public void run() { 113 cacheEnabledTags(); 114 } 115 }); 116 } 117 118 private Trace() { 119 } 120 121 /** 122 * Caches a copy of the enabled-tag bits. The "master" copy is held by the native code, 123 * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property. 124 * <p> 125 * If the native code hasn't yet read the property, we will cause it to do one-time 126 * initialization. We don't want to do this during class init, because this class is 127 * preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote 128 * doesn't see the system-property update broadcasts.) 129 * <p> 130 * We want to defer initialization until the first use by an app, post-zygote. 131 * <p> 132 * We're okay if multiple threads call here simultaneously -- the native state is 133 * synchronized, and sEnabledTags is volatile (prevents word tearing). 134 */ 135 private static long cacheEnabledTags() { 136 long tags = nativeGetEnabledTags(); 137 sEnabledTags = tags; 138 return tags; 139 } 140 141 /** 142 * Returns true if a trace tag is enabled. 143 * 144 * @param traceTag The trace tag to check. 145 * @return True if the trace tag is valid. 146 * 147 * @hide 148 */ 149 public static boolean isTagEnabled(long traceTag) { 150 long tags = sEnabledTags; 151 if (tags == TRACE_TAG_NOT_READY) { 152 tags = cacheEnabledTags(); 153 } 154 return (tags & traceTag) != 0; 155 } 156 157 /** 158 * Writes trace message to indicate the value of a given counter. 159 * 160 * @param traceTag The trace tag. 161 * @param counterName The counter name to appear in the trace. 162 * @param counterValue The counter value. 163 * 164 * @hide 165 */ 166 public static void traceCounter(long traceTag, String counterName, int counterValue) { 167 if (isTagEnabled(traceTag)) { 168 nativeTraceCounter(traceTag, counterName, counterValue); 169 } 170 } 171 172 /** 173 * Set whether application tracing is allowed for this process. This is intended to be set 174 * once at application start-up time based on whether the application is debuggable. 175 * 176 * @hide 177 */ 178 public static void setAppTracingAllowed(boolean allowed) { 179 nativeSetAppTracingAllowed(allowed); 180 181 // Setting whether app tracing is allowed may change the tags, so we update the cached 182 // tags here. 183 cacheEnabledTags(); 184 } 185 186 /** 187 * Set whether tracing is enabled in this process. Tracing is disabled shortly after Zygote 188 * initializes and re-enabled after processes fork from Zygote. This is done because Zygote 189 * has no way to be notified about changes to the tracing tags, and if Zygote ever reads and 190 * caches the tracing tags, forked processes will inherit those stale tags. 191 * 192 * @hide 193 */ 194 public static void setTracingEnabled(boolean enabled) { 195 nativeSetTracingEnabled(enabled); 196 197 // Setting whether tracing is enabled may change the tags, so we update the cached tags 198 // here. 199 cacheEnabledTags(); 200 } 201 202 /** 203 * Writes a trace message to indicate that a given section of code has 204 * begun. Must be followed by a call to {@link #traceEnd} using the same 205 * tag. 206 * 207 * @param traceTag The trace tag. 208 * @param methodName The method name to appear in the trace. 209 * 210 * @hide 211 */ 212 public static void traceBegin(long traceTag, String methodName) { 213 if (isTagEnabled(traceTag)) { 214 nativeTraceBegin(traceTag, methodName); 215 } 216 } 217 218 /** 219 * Writes a trace message to indicate that the current method has ended. 220 * Must be called exactly once for each call to {@link #traceBegin} using the same tag. 221 * 222 * @param traceTag The trace tag. 223 * 224 * @hide 225 */ 226 public static void traceEnd(long traceTag) { 227 if (isTagEnabled(traceTag)) { 228 nativeTraceEnd(traceTag); 229 } 230 } 231 232 /** 233 * Writes a trace message to indicate that a given section of code has 234 * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same 235 * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)}, 236 * asynchronous events do not need to be nested. The name and cookie used to 237 * begin an event must be used to end it. 238 * 239 * @param traceTag The trace tag. 240 * @param methodName The method name to appear in the trace. 241 * @param cookie Unique identifier for distinguishing simultaneous events 242 * 243 * @hide 244 */ 245 public static void asyncTraceBegin(long traceTag, String methodName, int cookie) { 246 if (isTagEnabled(traceTag)) { 247 nativeAsyncTraceBegin(traceTag, methodName, cookie); 248 } 249 } 250 251 /** 252 * Writes a trace message to indicate that the current method has ended. 253 * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)} 254 * using the same tag, name and cookie. 255 * 256 * @param traceTag The trace tag. 257 * @param methodName The method name to appear in the trace. 258 * @param cookie Unique identifier for distinguishing simultaneous events 259 * 260 * @hide 261 */ 262 public static void asyncTraceEnd(long traceTag, String methodName, int cookie) { 263 if (isTagEnabled(traceTag)) { 264 nativeAsyncTraceEnd(traceTag, methodName, cookie); 265 } 266 } 267 268 /** 269 * Writes a trace message to indicate that a given section of code has begun. This call must 270 * be followed by a corresponding call to {@link #endSection()} on the same thread. 271 * 272 * <p class="note"> At this time the vertical bar character '|', newline character '\n', and 273 * null character '\0' are used internally by the tracing mechanism. If sectionName contains 274 * these characters they will be replaced with a space character in the trace. 275 * 276 * @param sectionName The name of the code section to appear in the trace. This may be at 277 * most 127 Unicode code units long. 278 */ 279 public static void beginSection(String sectionName) { 280 if (isTagEnabled(TRACE_TAG_APP)) { 281 if (sectionName.length() > MAX_SECTION_NAME_LEN) { 282 throw new IllegalArgumentException("sectionName is too long"); 283 } 284 nativeTraceBegin(TRACE_TAG_APP, sectionName); 285 } 286 } 287 288 /** 289 * Writes a trace message to indicate that a given section of code has ended. This call must 290 * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method 291 * will mark the end of the most recently begun section of code, so care must be taken to 292 * ensure that beginSection / endSection pairs are properly nested and called from the same 293 * thread. 294 */ 295 public static void endSection() { 296 if (isTagEnabled(TRACE_TAG_APP)) { 297 nativeTraceEnd(TRACE_TAG_APP); 298 } 299 } 300 } 301
