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    // They should also be added to frameworks/native/cmds/atrace/atrace.cpp.
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    /** @hide */
69    public static final long TRACE_TAG_RESOURCES = 1L << 13;
70    /** @hide */
71    public static final long TRACE_TAG_DALVIK = 1L << 14;
72    /** @hide */
73    public static final long TRACE_TAG_RS = 1L << 15;
74    /** @hide */
75    public static final long TRACE_TAG_BIONIC = 1L << 16;
76    /** @hide */
77    public static final long TRACE_TAG_POWER = 1L << 17;
78    /** @hide */
79    public static final long TRACE_TAG_PACKAGE_MANAGER = 1L << 18;
80    /** @hide */
81    public static final long TRACE_TAG_SYSTEM_SERVER = 1L << 19;
82    /** @hide */
83    public static final long TRACE_TAG_DATABASE = 1L << 20;
84
85    private static final long TRACE_TAG_NOT_READY = 1L << 63;
86    private static final int MAX_SECTION_NAME_LEN = 127;
87
88    // Must be volatile to avoid word tearing.
89    private static volatile long sEnabledTags = TRACE_TAG_NOT_READY;
90
91    private static native long nativeGetEnabledTags();
92    private static native void nativeTraceCounter(long tag, String name, int value);
93    private static native void nativeTraceBegin(long tag, String name);
94    private static native void nativeTraceEnd(long tag);
95    private static native void nativeAsyncTraceBegin(long tag, String name, int cookie);
96    private static native void nativeAsyncTraceEnd(long tag, String name, int cookie);
97    private static native void nativeSetAppTracingAllowed(boolean allowed);
98    private static native void nativeSetTracingEnabled(boolean allowed);
99
100    static {
101        // We configure two separate change callbacks, one in Trace.cpp and one here.  The
102        // native callback reads the tags from the system property, and this callback
103        // reads the value that the native code retrieved.  It's essential that the native
104        // callback executes first.
105        //
106        // The system provides ordering through a priority level.  Callbacks made through
107        // SystemProperties.addChangeCallback currently have a negative priority, while
108        // our native code is using a priority of zero.
109        SystemProperties.addChangeCallback(new Runnable() {
110            @Override public void run() {
111                cacheEnabledTags();
112            }
113        });
114    }
115
116    private Trace() {
117    }
118
119    /**
120     * Caches a copy of the enabled-tag bits.  The "master" copy is held by the native code,
121     * and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property.
122     * <p>
123     * If the native code hasn't yet read the property, we will cause it to do one-time
124     * initialization.  We don't want to do this during class init, because this class is
125     * preloaded, so all apps would be stuck with whatever the zygote saw.  (The zygote
126     * doesn't see the system-property update broadcasts.)
127     * <p>
128     * We want to defer initialization until the first use by an app, post-zygote.
129     * <p>
130     * We're okay if multiple threads call here simultaneously -- the native state is
131     * synchronized, and sEnabledTags is volatile (prevents word tearing).
132     */
133    private static long cacheEnabledTags() {
134        long tags = nativeGetEnabledTags();
135        sEnabledTags = tags;
136        return tags;
137    }
138
139    /**
140     * Returns true if a trace tag is enabled.
141     *
142     * @param traceTag The trace tag to check.
143     * @return True if the trace tag is valid.
144     *
145     * @hide
146     */
147    public static boolean isTagEnabled(long traceTag) {
148        long tags = sEnabledTags;
149        if (tags == TRACE_TAG_NOT_READY) {
150            tags = cacheEnabledTags();
151        }
152        return (tags & traceTag) != 0;
153    }
154
155    /**
156     * Writes trace message to indicate the value of a given counter.
157     *
158     * @param traceTag The trace tag.
159     * @param counterName The counter name to appear in the trace.
160     * @param counterValue The counter value.
161     *
162     * @hide
163     */
164    public static void traceCounter(long traceTag, String counterName, int counterValue) {
165        if (isTagEnabled(traceTag)) {
166            nativeTraceCounter(traceTag, counterName, counterValue);
167        }
168    }
169
170    /**
171     * Set whether application tracing is allowed for this process.  This is intended to be set
172     * once at application start-up time based on whether the application is debuggable.
173     *
174     * @hide
175     */
176    public static void setAppTracingAllowed(boolean allowed) {
177        nativeSetAppTracingAllowed(allowed);
178
179        // Setting whether app tracing is allowed may change the tags, so we update the cached
180        // tags here.
181        cacheEnabledTags();
182    }
183
184    /**
185     * Set whether tracing is enabled in this process.  Tracing is disabled shortly after Zygote
186     * initializes and re-enabled after processes fork from Zygote.  This is done because Zygote
187     * has no way to be notified about changes to the tracing tags, and if Zygote ever reads and
188     * caches the tracing tags, forked processes will inherit those stale tags.
189     *
190     * @hide
191     */
192    public static void setTracingEnabled(boolean enabled) {
193        nativeSetTracingEnabled(enabled);
194
195        // Setting whether tracing is enabled may change the tags, so we update the cached tags
196        // here.
197        cacheEnabledTags();
198    }
199
200    /**
201     * Writes a trace message to indicate that a given section of code has
202     * begun. Must be followed by a call to {@link #traceEnd} using the same
203     * tag.
204     *
205     * @param traceTag The trace tag.
206     * @param methodName The method name to appear in the trace.
207     *
208     * @hide
209     */
210    public static void traceBegin(long traceTag, String methodName) {
211        if (isTagEnabled(traceTag)) {
212            nativeTraceBegin(traceTag, methodName);
213        }
214    }
215
216    /**
217     * Writes a trace message to indicate that the current method has ended.
218     * Must be called exactly once for each call to {@link #traceBegin} using the same tag.
219     *
220     * @param traceTag The trace tag.
221     *
222     * @hide
223     */
224    public static void traceEnd(long traceTag) {
225        if (isTagEnabled(traceTag)) {
226            nativeTraceEnd(traceTag);
227        }
228    }
229
230    /**
231     * Writes a trace message to indicate that a given section of code has
232     * begun. Must be followed by a call to {@link #asyncTraceEnd} using the same
233     * tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)},
234     * asynchronous events do not need to be nested. The name and cookie used to
235     * begin an event must be used to end it.
236     *
237     * @param traceTag The trace tag.
238     * @param methodName The method name to appear in the trace.
239     * @param cookie Unique identifier for distinguishing simultaneous events
240     *
241     * @hide
242     */
243    public static void asyncTraceBegin(long traceTag, String methodName, int cookie) {
244        if (isTagEnabled(traceTag)) {
245            nativeAsyncTraceBegin(traceTag, methodName, cookie);
246        }
247    }
248
249    /**
250     * Writes a trace message to indicate that the current method has ended.
251     * Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)}
252     * using the same tag, name and cookie.
253     *
254     * @param traceTag The trace tag.
255     * @param methodName The method name to appear in the trace.
256     * @param cookie Unique identifier for distinguishing simultaneous events
257     *
258     * @hide
259     */
260    public static void asyncTraceEnd(long traceTag, String methodName, int cookie) {
261        if (isTagEnabled(traceTag)) {
262            nativeAsyncTraceEnd(traceTag, methodName, cookie);
263        }
264    }
265
266    /**
267     * Writes a trace message to indicate that a given section of code has begun. This call must
268     * be followed by a corresponding call to {@link #endSection()} on the same thread.
269     *
270     * <p class="note"> At this time the vertical bar character '|', newline character '\n', and
271     * null character '\0' are used internally by the tracing mechanism.  If sectionName contains
272     * these characters they will be replaced with a space character in the trace.
273     *
274     * @param sectionName The name of the code section to appear in the trace.  This may be at
275     * most 127 Unicode code units long.
276     */
277    public static void beginSection(String sectionName) {
278        if (isTagEnabled(TRACE_TAG_APP)) {
279            if (sectionName.length() > MAX_SECTION_NAME_LEN) {
280                throw new IllegalArgumentException("sectionName is too long");
281            }
282            nativeTraceBegin(TRACE_TAG_APP, sectionName);
283        }
284    }
285
286    /**
287     * Writes a trace message to indicate that a given section of code has ended. This call must
288     * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method
289     * will mark the end of the most recently begun section of code, so care must be taken to
290     * ensure that beginSection / endSection pairs are properly nested and called from the same
291     * thread.
292     */
293    public static void endSection() {
294        if (isTagEnabled(TRACE_TAG_APP)) {
295            nativeTraceEnd(TRACE_TAG_APP);
296        }
297    }
298}
299