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 import 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 */ 29 public 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 /** @hide */ 69 public static final long TRACE_TAG_DALVIK = 1L << 14; 70 71 private static final long TRACE_TAG_NOT_READY = 1L << 63; 72 private static final int MAX_SECTION_NAME_LEN = 127; 73 74 // Must be volatile to avoid word tearing. 75 private static volatile long sEnabledTags = TRACE_TAG_NOT_READY; 76 77 private static native long nativeGetEnabledTags(); 78 private static native void nativeTraceCounter(long tag, String name, int value); 79 private static native void nativeTraceBegin(long tag, String name); 80 private static native void nativeTraceEnd(long tag); 81 private static native void nativeAsyncTraceBegin(long tag, String name, int cookie); 82 private static native void nativeAsyncTraceEnd(long tag, String name, int cookie); 83 private static native void nativeSetAppTracingAllowed(boolean allowed); 84 private static native void nativeSetTracingEnabled(boolean allowed); 85 86 static { 87 // We configure two separate change callbacks, one in Trace.cpp and one here. The 88 // native callback reads the tags from the system property, and this callback 89 // reads the value that the native code retrieved. It's essential that the native 90 // callback executes first. 91 // 92 // The system provides ordering through a priority level. Callbacks made through 93 // SystemProperties.addChangeCallback currently have a negative priority, while 94 // our native code is using a priority of zero. 95 SystemProperties.addChangeCallback(new Runnable() { 96 @Override public void run() { 97 cacheEnabledTags(); 98 } 99 }); 100 } 101 102 private Trace() { 103 } 104 105 /** 106 * Caches a copy of the enabled-tag bits. The "master" copy is held by the native code, 107 * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property. 108 * <p> 109 * If the native code hasn't yet read the property, we will cause it to do one-time 110 * initialization. We don't want to do this during class init, because this class is 111 * preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote 112 * doesn't see the system-property update broadcasts.) 113 * <p> 114 * We want to defer initialization until the first use by an app, post-zygote. 115 * <p> 116 * We're okay if multiple threads call here simultaneously -- the native state is 117 * synchronized, and sEnabledTags is volatile (prevents word tearing). 118 */ 119 private static long cacheEnabledTags() { 120 long tags = nativeGetEnabledTags(); 121 sEnabledTags = tags; 122 return tags; 123 } 124 125 /** 126 * Returns true if a trace tag is enabled. 127 * 128 * @param traceTag The trace tag to check. 129 * @return True if the trace tag is valid. 130 * 131 * @hide 132 */ 133 public static boolean isTagEnabled(long traceTag) { 134 long tags = sEnabledTags; 135 if (tags == TRACE_TAG_NOT_READY) { 136 tags = cacheEnabledTags(); 137 } 138 return (tags & traceTag) != 0; 139 } 140 141 /** 142 * Writes trace message to indicate the value of a given counter. 143 * 144 * @param traceTag The trace tag. 145 * @param counterName The counter name to appear in the trace. 146 * @param counterValue The counter value. 147 * 148 * @hide 149 */ 150 public static void traceCounter(long traceTag, String counterName, int counterValue) { 151 if (isTagEnabled(traceTag)) { 152 nativeTraceCounter(traceTag, counterName, counterValue); 153 } 154 } 155 156 /** 157 * Set whether application tracing is allowed for this process. This is intended to be set 158 * once at application start-up time based on whether the application is debuggable. 159 * 160 * @hide 161 */ 162 public static void setAppTracingAllowed(boolean allowed) { 163 nativeSetAppTracingAllowed(allowed); 164 165 // Setting whether app tracing is allowed may change the tags, so we update the cached 166 // tags here. 167 cacheEnabledTags(); 168 } 169 170 /** 171 * Set whether tracing is enabled in this process. Tracing is disabled shortly after Zygote 172 * initializes and re-enabled after processes fork from Zygote. This is done because Zygote 173 * has no way to be notified about changes to the tracing tags, and if Zygote ever reads and 174 * caches the tracing tags, forked processes will inherit those stale tags. 175 * 176 * @hide 177 */ 178 public static void setTracingEnabled(boolean enabled) { 179 nativeSetTracingEnabled(enabled); 180 181 // Setting whether tracing is enabled may change the tags, so we update the cached tags 182 // here. 183 cacheEnabledTags(); 184 } 185 186 /** 187 * Writes a trace message to indicate that a given section of code has 188 * begun. Must be followed by a call to {@link #traceEnd} using the same 189 * tag. 190 * 191 * @param traceTag The trace tag. 192 * @param methodName The method name to appear in the trace. 193 * 194 * @hide 195 */ 196 public static void traceBegin(long traceTag, String methodName) { 197 if (isTagEnabled(traceTag)) { 198 nativeTraceBegin(traceTag, methodName); 199 } 200 } 201 202 /** 203 * Writes a trace message to indicate that the current method has ended. 204 * Must be called exactly once for each call to {@link #traceBegin} using the same tag. 205 * 206 * @param traceTag The trace tag. 207 * 208 * @hide 209 */ 210 public static void traceEnd(long traceTag) { 211 if (isTagEnabled(traceTag)) { 212 nativeTraceEnd(traceTag); 213 } 214 } 215 216 /** 217 * Writes a trace message to indicate that a given section of code has 218 * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same 219 * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)}, 220 * asynchronous events do not need to be nested. The name and cookie used to 221 * begin an event must be used to end it. 222 * 223 * @param traceTag The trace tag. 224 * @param methodName The method name to appear in the trace. 225 * @param cookie Unique identifier for distinguishing simultaneous events 226 * 227 * @hide 228 */ 229 public static void asyncTraceBegin(long traceTag, String methodName, int cookie) { 230 if (isTagEnabled(traceTag)) { 231 nativeAsyncTraceBegin(traceTag, methodName, cookie); 232 } 233 } 234 235 /** 236 * Writes a trace message to indicate that the current method has ended. 237 * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)} 238 * using the same tag, name and cookie. 239 * 240 * @param traceTag The trace tag. 241 * @param methodName The method name to appear in the trace. 242 * @param cookie Unique identifier for distinguishing simultaneous events 243 * 244 * @hide 245 */ 246 public static void asyncTraceEnd(long traceTag, String methodName, int cookie) { 247 if (isTagEnabled(traceTag)) { 248 nativeAsyncTraceEnd(traceTag, methodName, cookie); 249 } 250 } 251 252 /** 253 * Writes a trace message to indicate that a given section of code has begun. This call must 254 * be followed by a corresponding call to {@link #endSection()} on the same thread. 255 * 256 * <p class="note"> At this time the vertical bar character '|', newline character '\n', and 257 * null character '\0' are used internally by the tracing mechanism. If sectionName contains 258 * these characters they will be replaced with a space character in the trace. 259 * 260 * @param sectionName The name of the code section to appear in the trace. This may be at 261 * most 127 Unicode code units long. 262 */ 263 public static void beginSection(String sectionName) { 264 if (isTagEnabled(TRACE_TAG_APP)) { 265 if (sectionName.length() > MAX_SECTION_NAME_LEN) { 266 throw new IllegalArgumentException("sectionName is too long"); 267 } 268 nativeTraceBegin(TRACE_TAG_APP, sectionName); 269 } 270 } 271 272 /** 273 * Writes a trace message to indicate that a given section of code has ended. This call must 274 * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method 275 * will mark the end of the most recently begun section of code, so care must be taken to 276 * ensure that beginSection / endSection pairs are properly nested and called from the same 277 * thread. 278 */ 279 public static void endSection() { 280 if (isTagEnabled(TRACE_TAG_APP)) { 281 nativeTraceEnd(TRACE_TAG_APP); 282 } 283 } 284 } 285
