Trace.java revision 6090995951c6e2e4dcf38102f01793f8a94166e1
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 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 */ 30public 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 /** @hide */ 40 public static final long TRACE_TAG_NEVER = 0; 41 /** @hide */ 42 public static final long TRACE_TAG_ALWAYS = 1L << 0; 43 /** @hide */ 44 public static final long TRACE_TAG_GRAPHICS = 1L << 1; 45 /** @hide */ 46 public static final long TRACE_TAG_INPUT = 1L << 2; 47 /** @hide */ 48 public static final long TRACE_TAG_VIEW = 1L << 3; 49 /** @hide */ 50 public static final long TRACE_TAG_WEBVIEW = 1L << 4; 51 /** @hide */ 52 public static final long TRACE_TAG_WINDOW_MANAGER = 1L << 5; 53 /** @hide */ 54 public static final long TRACE_TAG_ACTIVITY_MANAGER = 1L << 6; 55 /** @hide */ 56 public static final long TRACE_TAG_SYNC_MANAGER = 1L << 7; 57 /** @hide */ 58 public static final long TRACE_TAG_AUDIO = 1L << 8; 59 /** @hide */ 60 public static final long TRACE_TAG_VIDEO = 1L << 9; 61 /** @hide */ 62 public static final long TRACE_TAG_CAMERA = 1L << 10; 63 /** @hide */ 64 public static final long TRACE_TAG_HAL = 1L << 11; 65 /** @hide */ 66 public static final long TRACE_TAG_APP = 1L << 12; 67 /** @hide */ 68 public static final long TRACE_TAG_RESOURCES = 1L << 13; 69 /** @hide */ 70 public static final long TRACE_TAG_DALVIK = 1L << 14; 71 /** @hide */ 72 public static final long TRACE_TAG_RS = 1L << 15; 73 74 private static final long TRACE_TAG_NOT_READY = 1L << 63; 75 private static final int MAX_SECTION_NAME_LEN = 127; 76 77 // Must be volatile to avoid word tearing. 78 private static volatile long sEnabledTags = TRACE_TAG_NOT_READY; 79 80 private static native long nativeGetEnabledTags(); 81 private static native void nativeTraceCounter(long tag, String name, int value); 82 private static native void nativeTraceBegin(long tag, String name); 83 private static native void nativeTraceEnd(long tag); 84 private static native void nativeAsyncTraceBegin(long tag, String name, int cookie); 85 private static native void nativeAsyncTraceEnd(long tag, String name, int cookie); 86 private static native void nativeSetAppTracingAllowed(boolean allowed); 87 private static native void nativeSetTracingEnabled(boolean allowed); 88 89 static { 90 // We configure two separate change callbacks, one in Trace.cpp and one here. The 91 // native callback reads the tags from the system property, and this callback 92 // reads the value that the native code retrieved. It's essential that the native 93 // callback executes first. 94 // 95 // The system provides ordering through a priority level. Callbacks made through 96 // SystemProperties.addChangeCallback currently have a negative priority, while 97 // our native code is using a priority of zero. 98 SystemProperties.addChangeCallback(new Runnable() { 99 @Override public void run() { 100 cacheEnabledTags(); 101 } 102 }); 103 } 104 105 private Trace() { 106 } 107 108 /** 109 * Caches a copy of the enabled-tag bits. The "master" copy is held by the native code, 110 * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property. 111 * <p> 112 * If the native code hasn't yet read the property, we will cause it to do one-time 113 * initialization. We don't want to do this during class init, because this class is 114 * preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote 115 * doesn't see the system-property update broadcasts.) 116 * <p> 117 * We want to defer initialization until the first use by an app, post-zygote. 118 * <p> 119 * We're okay if multiple threads call here simultaneously -- the native state is 120 * synchronized, and sEnabledTags is volatile (prevents word tearing). 121 */ 122 private static long cacheEnabledTags() { 123 long tags = nativeGetEnabledTags(); 124 sEnabledTags = tags; 125 return tags; 126 } 127 128 /** 129 * Returns true if a trace tag is enabled. 130 * 131 * @param traceTag The trace tag to check. 132 * @return True if the trace tag is valid. 133 * 134 * @hide 135 */ 136 public static boolean isTagEnabled(long traceTag) { 137 long tags = sEnabledTags; 138 if (tags == TRACE_TAG_NOT_READY) { 139 tags = cacheEnabledTags(); 140 } 141 return (tags & traceTag) != 0; 142 } 143 144 /** 145 * Writes trace message to indicate the value of a given counter. 146 * 147 * @param traceTag The trace tag. 148 * @param counterName The counter name to appear in the trace. 149 * @param counterValue The counter value. 150 * 151 * @hide 152 */ 153 public static void traceCounter(long traceTag, String counterName, int counterValue) { 154 if (isTagEnabled(traceTag)) { 155 nativeTraceCounter(traceTag, counterName, counterValue); 156 } 157 } 158 159 /** 160 * Set whether application tracing is allowed for this process. This is intended to be set 161 * once at application start-up time based on whether the application is debuggable. 162 * 163 * @hide 164 */ 165 public static void setAppTracingAllowed(boolean allowed) { 166 nativeSetAppTracingAllowed(allowed); 167 168 // Setting whether app tracing is allowed may change the tags, so we update the cached 169 // tags here. 170 cacheEnabledTags(); 171 } 172 173 /** 174 * Set whether tracing is enabled in this process. Tracing is disabled shortly after Zygote 175 * initializes and re-enabled after processes fork from Zygote. This is done because Zygote 176 * has no way to be notified about changes to the tracing tags, and if Zygote ever reads and 177 * caches the tracing tags, forked processes will inherit those stale tags. 178 * 179 * @hide 180 */ 181 public static void setTracingEnabled(boolean enabled) { 182 nativeSetTracingEnabled(enabled); 183 184 // Setting whether tracing is enabled may change the tags, so we update the cached tags 185 // here. 186 cacheEnabledTags(); 187 } 188 189 /** 190 * Writes a trace message to indicate that a given section of code has 191 * begun. Must be followed by a call to {@link #traceEnd} using the same 192 * tag. 193 * 194 * @param traceTag The trace tag. 195 * @param methodName The method name to appear in the trace. 196 * 197 * @hide 198 */ 199 public static void traceBegin(long traceTag, String methodName) { 200 if (isTagEnabled(traceTag)) { 201 nativeTraceBegin(traceTag, methodName); 202 } 203 } 204 205 /** 206 * Writes a trace message to indicate that the current method has ended. 207 * Must be called exactly once for each call to {@link #traceBegin} using the same tag. 208 * 209 * @param traceTag The trace tag. 210 * 211 * @hide 212 */ 213 public static void traceEnd(long traceTag) { 214 if (isTagEnabled(traceTag)) { 215 nativeTraceEnd(traceTag); 216 } 217 } 218 219 /** 220 * Writes a trace message to indicate that a given section of code has 221 * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same 222 * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)}, 223 * asynchronous events do not need to be nested. The name and cookie used to 224 * begin an event must be used to end it. 225 * 226 * @param traceTag The trace tag. 227 * @param methodName The method name to appear in the trace. 228 * @param cookie Unique identifier for distinguishing simultaneous events 229 * 230 * @hide 231 */ 232 public static void asyncTraceBegin(long traceTag, String methodName, int cookie) { 233 if (isTagEnabled(traceTag)) { 234 nativeAsyncTraceBegin(traceTag, methodName, cookie); 235 } 236 } 237 238 /** 239 * Writes a trace message to indicate that the current method has ended. 240 * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)} 241 * using the same tag, name and cookie. 242 * 243 * @param traceTag The trace tag. 244 * @param methodName The method name to appear in the trace. 245 * @param cookie Unique identifier for distinguishing simultaneous events 246 * 247 * @hide 248 */ 249 public static void asyncTraceEnd(long traceTag, String methodName, int cookie) { 250 if (isTagEnabled(traceTag)) { 251 nativeAsyncTraceEnd(traceTag, methodName, cookie); 252 } 253 } 254 255 /** 256 * Writes a trace message to indicate that a given section of code has begun. This call must 257 * be followed by a corresponding call to {@link #endSection()} on the same thread. 258 * 259 * <p class="note"> At this time the vertical bar character '|', newline character '\n', and 260 * null character '\0' are used internally by the tracing mechanism. If sectionName contains 261 * these characters they will be replaced with a space character in the trace. 262 * 263 * @param sectionName The name of the code section to appear in the trace. This may be at 264 * most 127 Unicode code units long. 265 */ 266 public static void beginSection(String sectionName) { 267 if (isTagEnabled(TRACE_TAG_APP)) { 268 if (sectionName.length() > MAX_SECTION_NAME_LEN) { 269 throw new IllegalArgumentException("sectionName is too long"); 270 } 271 nativeTraceBegin(TRACE_TAG_APP, sectionName); 272 } 273 } 274 275 /** 276 * Writes a trace message to indicate that a given section of code has ended. This call must 277 * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method 278 * will mark the end of the most recently begun section of code, so care must be taken to 279 * ensure that beginSection / endSection pairs are properly nested and called from the same 280 * thread. 281 */ 282 public static void endSection() { 283 if (isTagEnabled(TRACE_TAG_APP)) { 284 nativeTraceEnd(TRACE_TAG_APP); 285 } 286 } 287} 288