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/*
* 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;
import android.util.Log;
/**
* Writes trace events to the kernel trace buffer. These trace events can be
* collected using the "atrace" program for offline analysis.
*
* 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 processes.
*
* @hide
*/
public final class Trace {
private static final String TAG = "Trace";
// These tags must be kept in sync with frameworks/native/include/utils/Trace.h.
public static final long TRACE_TAG_NEVER = 0;
public static final long TRACE_TAG_ALWAYS = 1L << 0;
public static final long TRACE_TAG_GRAPHICS = 1L << 1;
public static final long TRACE_TAG_INPUT = 1L << 2;
public static final long TRACE_TAG_VIEW = 1L << 3;
public static final long TRACE_TAG_WEBVIEW = 1L << 4;
public static final long TRACE_TAG_WINDOW_MANAGER = 1L << 5;
public static final long TRACE_TAG_ACTIVITY_MANAGER = 1L << 6;
public static final long TRACE_TAG_SYNC_MANAGER = 1L << 7;
public static final long TRACE_TAG_AUDIO = 1L << 8;
public static final long TRACE_TAG_VIDEO = 1L << 9;
public static final long TRACE_TAG_CAMERA = 1L << 10;
private static final long TRACE_TAG_NOT_READY = 1L << 63;
public static final int TRACE_FLAGS_START_BIT = 1;
public static final String[] TRACE_TAGS = {
"Graphics", "Input", "View", "WebView", "Window Manager",
"Activity Manager", "Sync Manager", "Audio", "Video", "Camera",
};
public static final String PROPERTY_TRACE_TAG_ENABLEFLAGS = "debug.atrace.tags.enableflags";
// 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);
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();
if (tags == TRACE_TAG_NOT_READY) {
Log.w(TAG, "Unexpected value from nativeGetEnabledTags: " + tags);
// keep going
}
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.
*/
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.
*/
public static void traceCounter(long traceTag, String counterName, int counterValue) {
if (isTagEnabled(traceTag)) {
nativeTraceCounter(traceTag, counterName, counterValue);
}
}
/**
* Writes a trace message to indicate that a given method 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.
*/
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.
*/
public static void traceEnd(long traceTag) {
if (isTagEnabled(traceTag)) {
nativeTraceEnd(traceTag);
}
}
}
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