/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.os;
/**
* Writes trace events to the system trace buffer. These trace events can be
* collected and visualized using the Systrace tool.
*
* <p>This tracing mechanism is independent of the method tracing mechanism
* offered by {@link Debug#startMethodTracing}. In particular, it enables
* tracing of events that occur across multiple processes.
* <p>For information about using the Systrace tool, read <a
* href="{@docRoot}tools/debugging/systrace.html">Analyzing Display and Performance
* with Systrace</a>.
*/
public final class Trace {
/*
* Writes trace events to the kernel trace buffer. These trace events can be
* collected using the "atrace" program for offline analysis.
*/
private static final String TAG = "Trace";
// These tags must be kept in sync with system/core/include/cutils/trace.h.
// They should also be added to frameworks/native/cmds/atrace/atrace.cpp.
/** @hide */
public static final long TRACE_TAG_NEVER = 0;
/** @hide */
public static final long TRACE_TAG_ALWAYS = 1L << 0;
/** @hide */
public static final long TRACE_TAG_GRAPHICS = 1L << 1;
/** @hide */
public static final long TRACE_TAG_INPUT = 1L << 2;
/** @hide */
public static final long TRACE_TAG_VIEW = 1L << 3;
/** @hide */
public static final long TRACE_TAG_WEBVIEW = 1L << 4;
/** @hide */
public static final long TRACE_TAG_WINDOW_MANAGER = 1L << 5;
/** @hide */
public static final long TRACE_TAG_ACTIVITY_MANAGER = 1L << 6;
/** @hide */
public static final long TRACE_TAG_SYNC_MANAGER = 1L << 7;
/** @hide */
public static final long TRACE_TAG_AUDIO = 1L << 8;
/** @hide */
public static final long TRACE_TAG_VIDEO = 1L << 9;
/** @hide */
public static final long TRACE_TAG_CAMERA = 1L << 10;
/** @hide */
public static final long TRACE_TAG_HAL = 1L << 11;
/** @hide */
public static final long TRACE_TAG_APP = 1L << 12;
/** @hide */
public static final long TRACE_TAG_RESOURCES = 1L << 13;
/** @hide */
public static final long TRACE_TAG_DALVIK = 1L << 14;
/** @hide */
public static final long TRACE_TAG_RS = 1L << 15;
/** @hide */
public static final long TRACE_TAG_BIONIC = 1L << 16;
/** @hide */
public static final long TRACE_TAG_POWER = 1L << 17;
private static final long TRACE_TAG_NOT_READY = 1L << 63;
private static final int MAX_SECTION_NAME_LEN = 127;
// Must be volatile to avoid word tearing.
private static volatile long sEnabledTags = TRACE_TAG_NOT_READY;
private static native long nativeGetEnabledTags();
private static native void nativeTraceCounter(long tag, String name, int value);
private static native void nativeTraceBegin(long tag, String name);
private static native void nativeTraceEnd(long tag);
private static native void nativeAsyncTraceBegin(long tag, String name, int cookie);
private static native void nativeAsyncTraceEnd(long tag, String name, int cookie);
private static native void nativeSetAppTracingAllowed(boolean allowed);
private static native void nativeSetTracingEnabled(boolean allowed);
static {
// We configure two separate change callbacks, one in Trace.cpp and one here. The
// native callback reads the tags from the system property, and this callback
// reads the value that the native code retrieved. It's essential that the native
// callback executes first.
//
// The system provides ordering through a priority level. Callbacks made through
// SystemProperties.addChangeCallback currently have a negative priority, while
// our native code is using a priority of zero.
SystemProperties.addChangeCallback(new Runnable() {
@Override public void run() {
cacheEnabledTags();
}
});
}
private Trace() {
}
/**
* Caches a copy of the enabled-tag bits. The "master" copy is held by the native code,
* and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property.
* <p>
* If the native code hasn't yet read the property, we will cause it to do one-time
* initialization. We don't want to do this during class init, because this class is
* preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote
* doesn't see the system-property update broadcasts.)
* <p>
* We want to defer initialization until the first use by an app, post-zygote.
* <p>
* We're okay if multiple threads call here simultaneously -- the native state is
* synchronized, and sEnabledTags is volatile (prevents word tearing).
*/
private static long cacheEnabledTags() {
long tags = nativeGetEnabledTags();
sEnabledTags = tags;
return tags;
}
/**
* Returns true if a trace tag is enabled.
*
* @param traceTag The trace tag to check.
* @return True if the trace tag is valid.
*
* @hide
*/
public static boolean isTagEnabled(long traceTag) {
long tags = sEnabledTags;
if (tags == TRACE_TAG_NOT_READY) {
tags = cacheEnabledTags();
}
return (tags & traceTag) != 0;
}
/**
* Writes trace message to indicate the value of a given counter.
*
* @param traceTag The trace tag.
* @param counterName The counter name to appear in the trace.
* @param counterValue The counter value.
*
* @hide
*/
public static void traceCounter(long traceTag, String counterName, int counterValue) {
if (isTagEnabled(traceTag)) {
nativeTraceCounter(traceTag, counterName, counterValue);
}
}
/**
* Set whether application tracing is allowed for this process. This is intended to be set
* once at application start-up time based on whether the application is debuggable.
*
* @hide
*/
public static void setAppTracingAllowed(boolean allowed) {
nativeSetAppTracingAllowed(allowed);
// Setting whether app tracing is allowed may change the tags, so we update the cached
// tags here.
cacheEnabledTags();
}
/**
* Set whether tracing is enabled in this process. Tracing is disabled shortly after Zygote
* initializes and re-enabled after processes fork from Zygote. This is done because Zygote
* has no way to be notified about changes to the tracing tags, and if Zygote ever reads and
* caches the tracing tags, forked processes will inherit those stale tags.
*
* @hide
*/
public static void setTracingEnabled(boolean enabled) {
nativeSetTracingEnabled(enabled);
// Setting whether tracing is enabled may change the tags, so we update the cached tags
// here.
cacheEnabledTags();
}
/**
* Writes a trace message to indicate that a given section of code has
* begun. Must be followed by a call to {@link #traceEnd} using the same
* tag.
*
* @param traceTag The trace tag.
* @param methodName The method name to appear in the trace.
*
* @hide
*/
public static void traceBegin(long traceTag, String methodName) {
if (isTagEnabled(traceTag)) {
nativeTraceBegin(traceTag, methodName);
}
}
/**
* Writes a trace message to indicate that the current method has ended.
* Must be called exactly once for each call to {@link #traceBegin} using the same tag.
*
* @param traceTag The trace tag.
*
* @hide
*/
public static void traceEnd(long traceTag) {
if (isTagEnabled(traceTag)) {
nativeTraceEnd(traceTag);
}
}
/**
* Writes a trace message to indicate that a given section of code has
* begun. Must be followed by a call to {@link #asyncTraceEnd} using the same
* tag. Unlike {@link #traceBegin(long, String)} and {@link #traceEnd(long)},
* asynchronous events do not need to be nested. The name and cookie used to
* begin an event must be used to end it.
*
* @param traceTag The trace tag.
* @param methodName The method name to appear in the trace.
* @param cookie Unique identifier for distinguishing simultaneous events
*
* @hide
*/
public static void asyncTraceBegin(long traceTag, String methodName, int cookie) {
if (isTagEnabled(traceTag)) {
nativeAsyncTraceBegin(traceTag, methodName, cookie);
}
}
/**
* Writes a trace message to indicate that the current method has ended.
* Must be called exactly once for each call to {@link #asyncTraceBegin(long, String, int)}
* using the same tag, name and cookie.
*
* @param traceTag The trace tag.
* @param methodName The method name to appear in the trace.
* @param cookie Unique identifier for distinguishing simultaneous events
*
* @hide
*/
public static void asyncTraceEnd(long traceTag, String methodName, int cookie) {
if (isTagEnabled(traceTag)) {
nativeAsyncTraceEnd(traceTag, methodName, cookie);
}
}
/**
* Writes a trace message to indicate that a given section of code has begun. This call must
* be followed by a corresponding call to {@link #endSection()} on the same thread.
*
* <p class="note"> At this time the vertical bar character '|', newline character '\n', and
* null character '\0' are used internally by the tracing mechanism. If sectionName contains
* these characters they will be replaced with a space character in the trace.
*
* @param sectionName The name of the code section to appear in the trace. This may be at
* most 127 Unicode code units long.
*/
public static void beginSection(String sectionName) {
if (isTagEnabled(TRACE_TAG_APP)) {
if (sectionName.length() > MAX_SECTION_NAME_LEN) {
throw new IllegalArgumentException("sectionName is too long");
}
nativeTraceBegin(TRACE_TAG_APP, sectionName);
}
}
/**
* Writes a trace message to indicate that a given section of code has ended. This call must
* be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method
* will mark the end of the most recently begun section of code, so care must be taken to
* ensure that beginSection / endSection pairs are properly nested and called from the same
* thread.
*/
public static void endSection() {
if (isTagEnabled(TRACE_TAG_APP)) {
nativeTraceEnd(TRACE_TAG_APP);
}
}
}
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