Trace.java revision 9425f923fae8977d09d924436148d3808032ea98
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 * 29 * @hide 30 */ 31public final class Trace { 32 /* 33 * Writes trace events to the kernel trace buffer. These trace events can be 34 * collected using the "atrace" program for offline analysis. 35 */ 36 37 private static final String TAG = "Trace"; 38 39 // These tags must be kept in sync with system/core/include/cutils/trace.h. 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 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 83 static { 84 // We configure two separate change callbacks, one in Trace.cpp and one here. The 85 // native callback reads the tags from the system property, and this callback 86 // reads the value that the native code retrieved. It's essential that the native 87 // callback executes first. 88 // 89 // The system provides ordering through a priority level. Callbacks made through 90 // SystemProperties.addChangeCallback currently have a negative priority, while 91 // our native code is using a priority of zero. 92 SystemProperties.addChangeCallback(new Runnable() { 93 @Override public void run() { 94 cacheEnabledTags(); 95 } 96 }); 97 } 98 99 private Trace() { 100 } 101 102 /** 103 * Caches a copy of the enabled-tag bits. The "master" copy is held by the native code, 104 * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property. 105 * <p> 106 * If the native code hasn't yet read the property, we will cause it to do one-time 107 * initialization. We don't want to do this during class init, because this class is 108 * preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote 109 * doesn't see the system-property update broadcasts.) 110 * <p> 111 * We want to defer initialization until the first use by an app, post-zygote. 112 * <p> 113 * We're okay if multiple threads call here simultaneously -- the native state is 114 * synchronized, and sEnabledTags is volatile (prevents word tearing). 115 */ 116 private static long cacheEnabledTags() { 117 long tags = nativeGetEnabledTags(); 118 if (tags == TRACE_TAG_NOT_READY) { 119 Log.w(TAG, "Unexpected value from nativeGetEnabledTags: " + tags); 120 // keep going 121 } 122 sEnabledTags = tags; 123 return tags; 124 } 125 126 /** 127 * Returns true if a trace tag is enabled. 128 * 129 * @param traceTag The trace tag to check. 130 * @return True if the trace tag is valid. 131 * 132 * @hide 133 */ 134 public static boolean isTagEnabled(long traceTag) { 135 long tags = sEnabledTags; 136 if (tags == TRACE_TAG_NOT_READY) { 137 tags = cacheEnabledTags(); 138 } 139 return (tags & traceTag) != 0; 140 } 141 142 /** 143 * Writes trace message to indicate the value of a given counter. 144 * 145 * @param traceTag The trace tag. 146 * @param counterName The counter name to appear in the trace. 147 * @param counterValue The counter value. 148 * 149 * @hide 150 */ 151 public static void traceCounter(long traceTag, String counterName, int counterValue) { 152 if (isTagEnabled(traceTag)) { 153 nativeTraceCounter(traceTag, counterName, counterValue); 154 } 155 } 156 157 /** 158 * Set whether application tracing is allowed for this process. This is intended to be set 159 * once at application start-up time based on whether the application is debuggable. 160 * 161 * @hide 162 */ 163 public static void setAppTracingAllowed(boolean allowed) { 164 nativeSetAppTracingAllowed(allowed); 165 166 // Setting whether app tracing is allowed may change the tags, so we update the cached 167 // tags here. 168 cacheEnabledTags(); 169 } 170 171 /** 172 * Writes a trace message to indicate that a given section of code has 173 * begun. Must be followed by a call to {@link #traceEnd} using the same 174 * tag. 175 * 176 * @param traceTag The trace tag. 177 * @param methodName The method name to appear in the trace. 178 * 179 * @hide 180 */ 181 public static void traceBegin(long traceTag, String methodName) { 182 if (isTagEnabled(traceTag)) { 183 nativeTraceBegin(traceTag, methodName); 184 } 185 } 186 187 /** 188 * Writes a trace message to indicate that the current method has ended. 189 * Must be called exactly once for each call to {@link #traceBegin} using the same tag. 190 * 191 * @param traceTag The trace tag. 192 * 193 * @hide 194 */ 195 public static void traceEnd(long traceTag) { 196 if (isTagEnabled(traceTag)) { 197 nativeTraceEnd(traceTag); 198 } 199 } 200 201 /** 202 * Writes a trace message to indicate that a given section of code has 203 * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same 204 * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)}, 205 * asynchronous events do not need to be nested. The name and cookie used to 206 * begin an event must be used to end it. 207 * 208 * @param traceTag The trace tag. 209 * @param methodName The method name to appear in the trace. 210 * @param cookie Unique identifier for distinguishing simultaneous events 211 * 212 * @hide 213 */ 214 public static void asyncTraceBegin(long traceTag, String methodName, int cookie) { 215 if (isTagEnabled(traceTag)) { 216 nativeAsyncTraceBegin(traceTag, methodName, cookie); 217 } 218 } 219 220 /** 221 * Writes a trace message to indicate that the current method has ended. 222 * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)} 223 * using the same tag, name and cookie. 224 * 225 * @param traceTag The trace tag. 226 * @param methodName The method name to appear in the trace. 227 * @param cookie Unique identifier for distinguishing simultaneous events 228 * 229 * @hide 230 */ 231 public static void asyncTraceEnd(long traceTag, String methodName, int cookie) { 232 if (isTagEnabled(traceTag)) { 233 nativeAsyncTraceEnd(traceTag, methodName, cookie); 234 } 235 } 236 237 /** 238 * Writes a trace message to indicate that a given section of code has begun. This call must 239 * be followed by a corresponding call to {@link #traceEnd()} on the same thread. 240 * 241 * <p class="note"> At this time the vertical bar character '|', newline character '\n', and 242 * null character '\0' are used internally by the tracing mechanism. If sectionName contains 243 * these characters they will be replaced with a space character in the trace. 244 * 245 * @param sectionName The name of the code section to appear in the trace. This may be at 246 * most 127 Unicode code units long. 247 * 248 * @hide 249 */ 250 public static void traceBegin(String sectionName) { 251 if (isTagEnabled(TRACE_TAG_APP)) { 252 if (sectionName.length() > MAX_SECTION_NAME_LEN) { 253 throw new IllegalArgumentException("sectionName is too long"); 254 } 255 nativeTraceBegin(TRACE_TAG_APP, sectionName); 256 } 257 } 258 259 /** 260 * Writes a trace message to indicate that a given section of code has ended. This call must 261 * be preceeded by a corresponding call to {@link #traceBegin(String)}. Calling this method 262 * will mark the end of the most recently begun section of code, so care must be taken to 263 * ensure that traceBegin / traceEnd pairs are properly nested and called from the same thread. 264 * 265 * @hide 266 */ 267 public static void traceEnd() { 268 if (isTagEnabled(TRACE_TAG_APP)) { 269 nativeTraceEnd(TRACE_TAG_APP); 270 } 271 } 272} 273