2 * Copyright (C) 2012 The Android Open Source Project
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
20 * Writes trace events to the system trace buffer. These trace events can be
21 * collected and visualized using the Systrace tool.
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
30 public final class Trace {
32 * Writes trace events to the kernel trace buffer. These trace events can be
33 * collected using the "atrace" program for offline analysis.
36 private static final String TAG = "Trace";
38 // These tags must be kept in sync with system/core/include/cutils/trace.h.
40 public static final long TRACE_TAG_NEVER = 0;
42 public static final long TRACE_TAG_ALWAYS = 1L << 0;
44 public static final long TRACE_TAG_GRAPHICS = 1L << 1;
46 public static final long TRACE_TAG_INPUT = 1L << 2;
48 public static final long TRACE_TAG_VIEW = 1L << 3;
50 public static final long TRACE_TAG_WEBVIEW = 1L << 4;
52 public static final long TRACE_TAG_WINDOW_MANAGER = 1L << 5;
54 public static final long TRACE_TAG_ACTIVITY_MANAGER = 1L << 6;
56 public static final long TRACE_TAG_SYNC_MANAGER = 1L << 7;
58 public static final long TRACE_TAG_AUDIO = 1L << 8;
60 public static final long TRACE_TAG_VIDEO = 1L << 9;
62 public static final long TRACE_TAG_CAMERA = 1L << 10;
64 public static final long TRACE_TAG_HAL = 1L << 11;
66 public static final long TRACE_TAG_APP = 1L << 12;
68 public static final long TRACE_TAG_RESOURCES = 1L << 13;
70 public static final long TRACE_TAG_DALVIK = 1L << 14;
72 public static final long TRACE_TAG_RS = 1L << 15;
74 public static final long TRACE_TAG_BIONIC = 1L << 16;
76 private static final long TRACE_TAG_NOT_READY = 1L << 63;
77 private static final int MAX_SECTION_NAME_LEN = 127;
79 // Must be volatile to avoid word tearing.
80 private static volatile long sEnabledTags = TRACE_TAG_NOT_READY;
82 private static native long nativeGetEnabledTags();
83 private static native void nativeTraceCounter(long tag, String name, int value);
84 private static native void nativeTraceBegin(long tag, String name);
85 private static native void nativeTraceEnd(long tag);
86 private static native void nativeAsyncTraceBegin(long tag, String name, int cookie);
87 private static native void nativeAsyncTraceEnd(long tag, String name, int cookie);
88 private static native void nativeSetAppTracingAllowed(boolean allowed);
89 private static native void nativeSetTracingEnabled(boolean allowed);
92 // We configure two separate change callbacks, one in Trace.cpp and one here. The
93 // native callback reads the tags from the system property, and this callback
94 // reads the value that the native code retrieved. It's essential that the native
95 // callback executes first.
97 // The system provides ordering through a priority level. Callbacks made through
98 // SystemProperties.addChangeCallback currently have a negative priority, while
99 // our native code is using a priority of zero.
100 SystemProperties.addChangeCallback(new Runnable() {
101 @Override public void run() {
111 * Caches a copy of the enabled-tag bits. The "master" copy is held by the native code,
112 * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property.
114 * If the native code hasn't yet read the property, we will cause it to do one-time
115 * initialization. We don't want to do this during class init, because this class is
116 * preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote
117 * doesn't see the system-property update broadcasts.)
119 * We want to defer initialization until the first use by an app, post-zygote.
121 * We're okay if multiple threads call here simultaneously -- the native state is
122 * synchronized, and sEnabledTags is volatile (prevents word tearing).
124 private static long cacheEnabledTags() {
125 long tags = nativeGetEnabledTags();
131 * Returns true if a trace tag is enabled.
133 * @param traceTag The trace tag to check.
134 * @return True if the trace tag is valid.
138 public static boolean isTagEnabled(long traceTag) {
139 long tags = sEnabledTags;
140 if (tags == TRACE_TAG_NOT_READY) {
141 tags = cacheEnabledTags();
143 return (tags & traceTag) != 0;
147 * Writes trace message to indicate the value of a given counter.
149 * @param traceTag The trace tag.
150 * @param counterName The counter name to appear in the trace.
151 * @param counterValue The counter value.
155 public static void traceCounter(long traceTag, String counterName, int counterValue) {
156 if (isTagEnabled(traceTag)) {
157 nativeTraceCounter(traceTag, counterName, counterValue);
162 * Set whether application tracing is allowed for this process. This is intended to be set
163 * once at application start-up time based on whether the application is debuggable.
167 public static void setAppTracingAllowed(boolean allowed) {
168 nativeSetAppTracingAllowed(allowed);
170 // Setting whether app tracing is allowed may change the tags, so we update the cached
176 * Set whether tracing is enabled in this process. Tracing is disabled shortly after Zygote
177 * initializes and re-enabled after processes fork from Zygote. This is done because Zygote
178 * has no way to be notified about changes to the tracing tags, and if Zygote ever reads and
179 * caches the tracing tags, forked processes will inherit those stale tags.
183 public static void setTracingEnabled(boolean enabled) {
184 nativeSetTracingEnabled(enabled);
186 // Setting whether tracing is enabled may change the tags, so we update the cached tags
192 * Writes a trace message to indicate that a given section of code has
193 * begun. Must be followed by a call to {@link #traceEnd} using the same
196 * @param traceTag The trace tag.
197 * @param methodName The method name to appear in the trace.
201 public static void traceBegin(long traceTag, String methodName) {
202 if (isTagEnabled(traceTag)) {
203 nativeTraceBegin(traceTag, methodName);
208 * Writes a trace message to indicate that the current method has ended.
209 * Must be called exactly once for each call to {@link #traceBegin} using the same tag.
211 * @param traceTag The trace tag.
215 public static void traceEnd(long traceTag) {
216 if (isTagEnabled(traceTag)) {
217 nativeTraceEnd(traceTag);
222 * Writes a trace message to indicate that a given section of code has
223 * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same
224 * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)},
225 * asynchronous events do not need to be nested. The name and cookie used to
226 * begin an event must be used to end it.
228 * @param traceTag The trace tag.
229 * @param methodName The method name to appear in the trace.
230 * @param cookie Unique identifier for distinguishing simultaneous events
234 public static void asyncTraceBegin(long traceTag, String methodName, int cookie) {
235 if (isTagEnabled(traceTag)) {
236 nativeAsyncTraceBegin(traceTag, methodName, cookie);
241 * Writes a trace message to indicate that the current method has ended.
242 * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)}
243 * using the same tag, name and cookie.
245 * @param traceTag The trace tag.
246 * @param methodName The method name to appear in the trace.
247 * @param cookie Unique identifier for distinguishing simultaneous events
251 public static void asyncTraceEnd(long traceTag, String methodName, int cookie) {
252 if (isTagEnabled(traceTag)) {
253 nativeAsyncTraceEnd(traceTag, methodName, cookie);
258 * Writes a trace message to indicate that a given section of code has begun. This call must
259 * be followed by a corresponding call to {@link #endSection()} on the same thread.
261 * <p class="note"> At this time the vertical bar character '|', newline character '\n', and
262 * null character '\0' are used internally by the tracing mechanism. If sectionName contains
263 * these characters they will be replaced with a space character in the trace.
265 * @param sectionName The name of the code section to appear in the trace. This may be at
266 * most 127 Unicode code units long.
268 public static void beginSection(String sectionName) {
269 if (isTagEnabled(TRACE_TAG_APP)) {
270 if (sectionName.length() > MAX_SECTION_NAME_LEN) {
271 throw new IllegalArgumentException("sectionName is too long");
273 nativeTraceBegin(TRACE_TAG_APP, sectionName);
278 * Writes a trace message to indicate that a given section of code has ended. This call must
279 * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method
280 * will mark the end of the most recently begun section of code, so care must be taken to
281 * ensure that beginSection / endSection pairs are properly nested and called from the same
284 public static void endSection() {
285 if (isTagEnabled(TRACE_TAG_APP)) {
286 nativeTraceEnd(TRACE_TAG_APP);