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 com.android.internal.os.Zygote; 20 21 import dalvik.annotation.optimization.FastNative; 22 23 /** 24 * Writes trace events to the system trace buffer. These trace events can be 25 * collected and visualized using the Systrace tool. 26 * 27 * <p>This tracing mechanism is independent of the method tracing mechanism 28 * offered by {@link Debug#startMethodTracing}. In particular, it enables 29 * tracing of events that occur across multiple processes. 30 * <p>For information about using the Systrace tool, read <a 31 * href="{@docRoot}tools/debugging/systrace.html">Analyzing Display and Performance 32 * with Systrace</a>. 33 */ 34 public final class Trace { 35 /* 36 * Writes trace events to the kernel trace buffer. These trace events can be 37 * collected using the "atrace" program for offline analysis. 38 */ 39 40 private static final String TAG = "Trace"; 41 42 // These tags must be kept in sync with system/core/include/cutils/trace.h. 43 // They should also be added to frameworks/native/cmds/atrace/atrace.cpp. 44 /** @hide */ 45 public static final long TRACE_TAG_NEVER = 0; 46 /** @hide */ 47 public static final long TRACE_TAG_ALWAYS = 1L << 0; 48 /** @hide */ 49 public static final long TRACE_TAG_GRAPHICS = 1L << 1; 50 /** @hide */ 51 public static final long TRACE_TAG_INPUT = 1L << 2; 52 /** @hide */ 53 public static final long TRACE_TAG_VIEW = 1L << 3; 54 /** @hide */ 55 public static final long TRACE_TAG_WEBVIEW = 1L << 4; 56 /** @hide */ 57 public static final long TRACE_TAG_WINDOW_MANAGER = 1L << 5; 58 /** @hide */ 59 public static final long TRACE_TAG_ACTIVITY_MANAGER = 1L << 6; 60 /** @hide */ 61 public static final long TRACE_TAG_SYNC_MANAGER = 1L << 7; 62 /** @hide */ 63 public static final long TRACE_TAG_AUDIO = 1L << 8; 64 /** @hide */ 65 public static final long TRACE_TAG_VIDEO = 1L << 9; 66 /** @hide */ 67 public static final long TRACE_TAG_CAMERA = 1L << 10; 68 /** @hide */ 69 public static final long TRACE_TAG_HAL = 1L << 11; 70 /** @hide */ 71 public static final long TRACE_TAG_APP = 1L << 12; 72 /** @hide */ 73 public static final long TRACE_TAG_RESOURCES = 1L << 13; 74 /** @hide */ 75 public static final long TRACE_TAG_DALVIK = 1L << 14; 76 /** @hide */ 77 public static final long TRACE_TAG_RS = 1L << 15; 78 /** @hide */ 79 public static final long TRACE_TAG_BIONIC = 1L << 16; 80 /** @hide */ 81 public static final long TRACE_TAG_POWER = 1L << 17; 82 /** @hide */ 83 public static final long TRACE_TAG_PACKAGE_MANAGER = 1L << 18; 84 /** @hide */ 85 public static final long TRACE_TAG_SYSTEM_SERVER = 1L << 19; 86 /** @hide */ 87 public static final long TRACE_TAG_DATABASE = 1L << 20; 88 /** @hide */ 89 public static final long TRACE_TAG_NETWORK = 1L << 21; 90 /** @hide */ 91 public static final long TRACE_TAG_ADB = 1L << 22; 92 93 private static final long TRACE_TAG_NOT_READY = 1L << 63; 94 private static final int MAX_SECTION_NAME_LEN = 127; 95 96 // Must be volatile to avoid word tearing. 97 private static volatile long sEnabledTags = TRACE_TAG_NOT_READY; 98 99 private static int sZygoteDebugFlags = 0; 100 101 private static native long nativeGetEnabledTags(); 102 private static native void nativeSetAppTracingAllowed(boolean allowed); 103 private static native void nativeSetTracingEnabled(boolean allowed); 104 105 @FastNative 106 private static native void nativeTraceCounter(long tag, String name, int value); 107 @FastNative 108 private static native void nativeTraceBegin(long tag, String name); 109 @FastNative 110 private static native void nativeTraceEnd(long tag); 111 @FastNative 112 private static native void nativeAsyncTraceBegin(long tag, String name, int cookie); 113 @FastNative 114 private static native void nativeAsyncTraceEnd(long tag, String name, int cookie); 115 116 static { 117 // We configure two separate change callbacks, one in Trace.cpp and one here. The 118 // native callback reads the tags from the system property, and this callback 119 // reads the value that the native code retrieved. It's essential that the native 120 // callback executes first. 121 // 122 // The system provides ordering through a priority level. Callbacks made through 123 // SystemProperties.addChangeCallback currently have a negative priority, while 124 // our native code is using a priority of zero. 125 SystemProperties.addChangeCallback(() -> { 126 cacheEnabledTags(); 127 if ((sZygoteDebugFlags & Zygote.DEBUG_JAVA_DEBUGGABLE) != 0) { 128 traceCounter(TRACE_TAG_ALWAYS, "java_debuggable", 1); 129 } 130 }); 131 } 132 133 private Trace() { 134 } 135 136 /** 137 * Caches a copy of the enabled-tag bits. The "master" copy is held by the native code, 138 * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property. 139 * <p> 140 * If the native code hasn't yet read the property, we will cause it to do one-time 141 * initialization. We don't want to do this during class init, because this class is 142 * preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote 143 * doesn't see the system-property update broadcasts.) 144 * <p> 145 * We want to defer initialization until the first use by an app, post-zygote. 146 * <p> 147 * We're okay if multiple threads call here simultaneously -- the native state is 148 * synchronized, and sEnabledTags is volatile (prevents word tearing). 149 */ 150 private static long cacheEnabledTags() { 151 long tags = nativeGetEnabledTags(); 152 sEnabledTags = tags; 153 return tags; 154 } 155 156 /** 157 * Returns true if a trace tag is enabled. 158 * 159 * @param traceTag The trace tag to check. 160 * @return True if the trace tag is valid. 161 * 162 * @hide 163 */ 164 public static boolean isTagEnabled(long traceTag) { 165 long tags = sEnabledTags; 166 if (tags == TRACE_TAG_NOT_READY) { 167 tags = cacheEnabledTags(); 168 } 169 return (tags & traceTag) != 0; 170 } 171 172 /** 173 * Writes trace message to indicate the value of a given counter. 174 * 175 * @param traceTag The trace tag. 176 * @param counterName The counter name to appear in the trace. 177 * @param counterValue The counter value. 178 * 179 * @hide 180 */ 181 public static void traceCounter(long traceTag, String counterName, int counterValue) { 182 if (isTagEnabled(traceTag)) { 183 nativeTraceCounter(traceTag, counterName, counterValue); 184 } 185 } 186 187 /** 188 * Set whether application tracing is allowed for this process. This is intended to be set 189 * once at application start-up time based on whether the application is debuggable. 190 * 191 * @hide 192 */ 193 public static void setAppTracingAllowed(boolean allowed) { 194 nativeSetAppTracingAllowed(allowed); 195 196 // Setting whether app tracing is allowed may change the tags, so we update the cached 197 // tags here. 198 cacheEnabledTags(); 199 } 200 201 /** 202 * Set whether tracing is enabled in this process. Tracing is disabled shortly after Zygote 203 * initializes and re-enabled after processes fork from Zygote. This is done because Zygote 204 * has no way to be notified about changes to the tracing tags, and if Zygote ever reads and 205 * caches the tracing tags, forked processes will inherit those stale tags. 206 * 207 * @hide 208 */ 209 public static void setTracingEnabled(boolean enabled, int debugFlags) { 210 nativeSetTracingEnabled(enabled); 211 sZygoteDebugFlags = debugFlags; 212 213 // Setting whether tracing is enabled may change the tags, so we update the cached tags 214 // here. 215 cacheEnabledTags(); 216 } 217 218 /** 219 * Writes a trace message to indicate that a given section of code has 220 * begun. Must be followed by a call to {@link #traceEnd} using the same 221 * tag. 222 * 223 * @param traceTag The trace tag. 224 * @param methodName The method name to appear in the trace. 225 * 226 * @hide 227 */ 228 public static void traceBegin(long traceTag, String methodName) { 229 if (isTagEnabled(traceTag)) { 230 nativeTraceBegin(traceTag, methodName); 231 } 232 } 233 234 /** 235 * Writes a trace message to indicate that the current method has ended. 236 * Must be called exactly once for each call to {@link #traceBegin} using the same tag. 237 * 238 * @param traceTag The trace tag. 239 * 240 * @hide 241 */ 242 public static void traceEnd(long traceTag) { 243 if (isTagEnabled(traceTag)) { 244 nativeTraceEnd(traceTag); 245 } 246 } 247 248 /** 249 * Writes a trace message to indicate that a given section of code has 250 * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same 251 * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)}, 252 * asynchronous events do not need to be nested. The name and cookie used to 253 * begin an event must be used to end it. 254 * 255 * @param traceTag The trace tag. 256 * @param methodName The method name to appear in the trace. 257 * @param cookie Unique identifier for distinguishing simultaneous events 258 * 259 * @hide 260 */ 261 public static void asyncTraceBegin(long traceTag, String methodName, int cookie) { 262 if (isTagEnabled(traceTag)) { 263 nativeAsyncTraceBegin(traceTag, methodName, cookie); 264 } 265 } 266 267 /** 268 * Writes a trace message to indicate that the current method has ended. 269 * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)} 270 * using the same tag, name and cookie. 271 * 272 * @param traceTag The trace tag. 273 * @param methodName The method name to appear in the trace. 274 * @param cookie Unique identifier for distinguishing simultaneous events 275 * 276 * @hide 277 */ 278 public static void asyncTraceEnd(long traceTag, String methodName, int cookie) { 279 if (isTagEnabled(traceTag)) { 280 nativeAsyncTraceEnd(traceTag, methodName, cookie); 281 } 282 } 283 284 /** 285 * Writes a trace message to indicate that a given section of code has begun. This call must 286 * be followed by a corresponding call to {@link #endSection()} on the same thread. 287 * 288 * <p class="note"> At this time the vertical bar character '|', newline character '\n', and 289 * null character '\0' are used internally by the tracing mechanism. If sectionName contains 290 * these characters they will be replaced with a space character in the trace. 291 * 292 * @param sectionName The name of the code section to appear in the trace. This may be at 293 * most 127 Unicode code units long. 294 */ 295 public static void beginSection(String sectionName) { 296 if (isTagEnabled(TRACE_TAG_APP)) { 297 if (sectionName.length() > MAX_SECTION_NAME_LEN) { 298 throw new IllegalArgumentException("sectionName is too long"); 299 } 300 nativeTraceBegin(TRACE_TAG_APP, sectionName); 301 } 302 } 303 304 /** 305 * Writes a trace message to indicate that a given section of code has ended. This call must 306 * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method 307 * will mark the end of the most recently begun section of code, so care must be taken to 308 * ensure that beginSection / endSection pairs are properly nested and called from the same 309 * thread. 310 */ 311 public static void endSection() { 312 if (isTagEnabled(TRACE_TAG_APP)) { 313 nativeTraceEnd(TRACE_TAG_APP); 314 } 315 } 316 } 317
