docs/html/guide/developing/tools/traceview.jd

page.title=Traceview: A Graphical Log Viewer
@jd:body

<p>Traceview is a graphical viewer for execution logs
saved by your application. The sections below describe how to use the program. </p>

<h2>Contents</h2>

<dl>
    <dt><a href="#creatingtracefiles">Creating Trace Files</a></dt>
    <dt><a href="#copyingfiles">Copying Trace Files to a Host Machine</a></dt>
    <dt><a href="#runningtraceview">Viewing Trace Files in Traceview</a></dt>
            <dd><a href="#timelinepanel">Timeline Panel</a></dd>
        	<dd><a href="#profilepanel">Profile Panel</a></dd>
    <dt><a href="#format">Traceview File Format</a></dd>
        	<dd><a href="#datafileformat">Data File Format</a><dd>
        	<dd><a href="#keyfileformat">Key File Format</a></dd>
	<dt><a href="#knownissues">Traceview Known Issues</a></dd>
    <dt><a href="#dmtracedump">Using dmtracedump</a></dt>
</dl>

<a name="creatingtracefiles"></a>

<h2>Creating Trace Files</h2>

<p>To use Traceview, you need to generate log files containing the trace information you want to analyze. To do that, you  include the {@link android.os.Debug}
  class in your code and call its methods to start and stop logging of trace information
  to disk. When your application quits, you can then use Traceview to examine the log files
  for useful run-time information such
  as method calls and run times. </p>
<p>To create the trace files, include the {@link android.os.Debug} class and call one
  of the {@link android.os.Debug#startMethodTracing() startMethodTracing()} methods. 
  In the call, you specify a base name for the trace files that the system generates. 
  To stop tracing, call {@link android.os.Debug#stopMethodTracing() stopMethodTracing()}.
  These methods start and stop method tracing across the entire virtual machine. For 
  example, you could call startMethodTracing() in your activity's onCreate()
  method, and call stopMethodTracing() in that activity's onDestroy() method.</p>

<pre>
    // start tracing to "/sdcard/calc.trace"
    Debug.startMethodTracing("calc");
    // ...
    // stop tracing
    Debug.stopMethodTracing();
</pre>

<p>When your application calls startMethodTracing(), the system creates a
file called <code>&lt;trace-base-name>.trace</code>.  This contains the
binary method trace data and a mapping table with thread and method names.</p>

<p>The system then begins buffering the generated trace data, until your application calls 
	stopMethodTracing(), at which time it writes the buffered data to the
	output file.
	If the system reaches the maximum buffer size before stopMethodTracing() 
	is called, the system stops tracing and sends a notification
	to the console. </p>

<p>Interpreted code will run more slowly when profiling is enabled.  Don't
try to generate absolute timings from the profiler results (i.e. "function
X takes 2.5 seconds to run").  The times are only
useful in relation to other profile output, so you can see if changes
have made the code faster or slower. </p>

<p>When using the Android emulator, you must create an SD card image upon which
the trace files will be written. For example, from the <code>/tools</code> directory, you 
can create an SD card image and mount it when launching the emulator like so:</p>
<pre>
<b>$</b> mksdcard 1024M ./imgcd 
<b>$</b> emulator -sdcard ./img
</pre>
<p>For more information, read about the 
<a href="{@docRoot}guide/developing/tools/othertools.html#mksdcard">mksdcard tool</a>.</p>
	
<p>The format of the trace files is described <a href="#format">later 
   in this document</a>. </p>

<a name="copyingfiles"></a>

<h2>Copying Trace Files to a Host Machine</h2>
<p>After your application has run and the system has created your trace files <code>&lt;trace-base-name>.trace</code>
    on a device or emulator, you must copy those files to your development computer.   You can use <code>adb pull</code> to copy
    the files. Here's an example that shows how to copy an example file,
    calc.trace, from the default location on the emulator to the /tmp directory on
the emulator host machine:</p>
<pre>adb pull /sdcard/calc.trace /tmp</pre>


<a name="runningtraceview"></a>

<h2>Viewing Trace Files in Traceview</h2>
<p>To run traceview and view the trace files, enter <code>traceview &lt;trace-base-name></code>.
    For example, to run Traceview on the example files copied in the previous section,
    you would use: </p>
    <pre>traceview /tmp/calc</pre>

	<p>Traceview loads the log files and displays their data in a window that has two panels:</p>
	<ul>
		<li>A <a href="#timelinepanel">timeline panel</a> -- describes when each thread
	    and method started and stopped</li>
    	<li>A <a href="#timelinepanel">profile panel</a> -- provides a summary of what happened inside a method</li>
	</ul>
	<p>The sections below provide addition information about the traceview output panes. </p>

<a name="timelinepanel"></a>

<h3>Timeline Panel  </h3>
<p>The image below shows a close up of the timeline panel. Each thread&rsquo;s
    execution is shown in its own row, with time increasing to the right. Each method
    is shown in another color (colors are reused in a round-robin fashion starting
    with the methods that have the most inclusive time). The thin lines underneath
    the first row show the extent (entry to exit) of all the calls to the selected
    method. The method in this case is LoadListener.nativeFinished() and it was
    selected in the profile view. </p>
<p><img src="/images/traceview_timeline.png" alt="Traceview timeline panel" width="893" height="284"></p>
<a name="profilepanel"></a>
<h3>Profile Panel</h3>
<p>The image below shows the profile pane. The profile pane shows a
    summary of all the time spent in a method. The table shows
    both the inclusive and exclusive times (as well as the percentage of the total
    time). Exclusive time is the time spent in the method. Inclusive time is the
    time spent in the method plus the time spent in any called functions. We refer
    to  calling methods as &quot;parents&quot; and called methods as &quot;children.&quot;
    When a method is selected (by clicking on it), it expands to show the parents
    and children. Parents are shown with a purple background and children
    with a yellow background. The last column in the table shows the number of calls
    to this method plus the number of recursive calls. The last column shows the
    number of calls out of the total number of calls made to that method. In this
    view, we can see that there were 14 calls to LoadListener.nativeFinished(); looking
    at the timeline panel shows that one of those calls took an unusually
    long time.</p>
<p><img src="/images/traceview_profile.png" alt="Traceview profile panel." width="892" height="630"></p>

<a name="format"></a>
<h2>Traceview File Format</h2>
<p>Tracing creates two distinct pieces of output: a <em>data</em> file,
    which holds the trace data, and a <em>key</em> file, which
    provides a mapping from binary identifiers to thread and method names.
	The files are concatenated when tracing completes, into a
	single <em>.trace</em> file. </p>

<p class="note"><strong>Note:</strong> The previous version of Traceview did not concatenate 
these files for you. If you have old key and data files that you'd still like to trace, you 
can concatenate them yourself with <code>cat mytrace.key mytrace.data > mytrace.trace</code>.</p>

<a name="datafileformat"></a>

<h3>Data File Format</h3>
<p>The data file is binary, structured as
    follows (all values are stored in little-endian order):</p>
<pre>* File format:
* header
* record 0
* record 1
* ...
*
* Header format:
* u4 magic 0x574f4c53 ('SLOW')
* u2 version
* u2 offset to data
* u8 start date/time in usec
*
* Record format:
* u1 thread ID
* u4 method ID | method action
* u4 time delta since start, in usec
</pre>
<p>The application is expected to parse all of the header fields, then seek
    to &quot;offset to data&quot; from the start of the file. From there it just
    reads
    9-byte records until EOF is reached.</p>
<p><em>u8 start date/time in usec</em> is the output from gettimeofday().
    It's mainly there so that you can tell if the output was generated yesterday
    or three months ago.</p>
<p><em>method action</em> sits in the two least-significant bits of the
    <em>method</em> word. The currently defined meanings are:    </p>
<ul>
    <li>0 - method entry </li>
    <li>1 - method exit </li>
    <li>2 - method &quot;exited&quot; when unrolled by exception handling </li>
    <li>3 - (reserved)</li>
</ul>
<p>An unsigned 32-bit integer can hold about 70 minutes of time in microseconds.
</p>

<a name="keyfileformat"></a>
	
<h3>Key File Format</h3>
<p>The key file is a plain text file divided into three sections. Each
    section starts with a keyword that begins with '*'. If you see a '*' at the start
    of a line, you have found the start of a new section.</p>
<p>An example file might look like this:</p>
<pre>*version
1
clock=global
*threads
1 main
6 JDWP Handler
5 Async GC
4 Reference Handler
3 Finalizer
2 Signal Handler
*methods
0x080f23f8 java/io/PrintStream write ([BII)V
0x080f25d4 java/io/PrintStream print (Ljava/lang/String;)V
0x080f27f4 java/io/PrintStream println (Ljava/lang/String;)V
0x080da620 java/lang/RuntimeException	&lt;init&gt;	()V
[...]
0x080f630c android/os/Debug startMethodTracing ()V
0x080f6350 android/os/Debug startMethodTracing (Ljava/lang/String;Ljava/lang/String;I)V
*end</pre>
<dl>
    <dt><em>version section</em></dt>
    <dd>The first line is the file version number, currently
        1.
        The second line, <code>clock=global</code>, indicates that we use a common
        clock across all threads. A future version may use per-thread CPU time counters
        that are independent for every thread.</dd>
    <dt><em>threads section</em></dt>
    <dd>One line per thread. Each line consists of two parts: the thread ID, followed
        by a tab, followed by the thread name. There are few restrictions on what
        a valid thread name is, so include everything to the end of the line.</dd>
    <dt><em>methods section </em></dt>
    <dd>One line per method entry or exit. A line consists of four pieces,
        separated by tab marks: <em>method-ID</em> [TAB] <em>class-name</em> [TAB] 
        <em>method-name</em> [TAB] 
        <em>signature</em> . Only
        the methods that were actually entered or exited are included in the list.
        Note that all three identifiers are required to uniquely identify a
        method.</dd>
</dl>
<p>Neither the threads nor methods sections are sorted.</p>

<a name="knownissues"></a>
<h2>Traceview Known Issues</h2>
<dl>
	<dt>Threads</dt>
	<dd>Traceview logging does not handle threads well, resulting in these two problems:
<ol>
  <li> If a thread exits during profiling, the thread name is not emitted; </li>
    <li>The VM reuses thread IDs. If a thread stops and another starts, they
        may get the same ID. </li>
</ol>
</dd>

<a name="dmtracedump"></a>

<h2>Using dmtracedump</h2>

<p>The Android SDK includes dmtracedump, a tool that gives you an alternate way 
	of generating graphical call-stack diagrams from trace log files. The tool 
	uses the Graphviz Dot utility to create the graphical output, so you need to 
	install Graphviz before running dmtracedump.</p>
	
<p>The dmtracedump tool generates the call stack data as a tree diagram, with each call 
	represented as a node. It shows call flow (from parent node to child nodes) using 
	arrows. The diagram below shows an example of dmtracedump output.</p>
	
<img src="{@docRoot}images/tracedump.png" width="485" height="401" style="margin-top:1em;"/>

<p style="margin-top:1em;">For each node, dmtracedump shows <code>&lt;ref> <em>callname</em> (&lt;inc-ms>,
	&lt;exc-ms>,&lt;numcalls>)</code>, where</p>

<ul>
		<li><code>&lt;ref></code> -- Call reference number, as used in trace logs</li>
		<li><code>&lt;inc-ms></code> -- Inclusive elapsed time (milliseconds spent in method, including all child methods)</li>
		<li><code>&lt;exc-ms></code> -- Exclusive elapsed time (milliseconds spent in method, not including any child methods)</li>
		<li><code>&lt;numcalls></code> -- Number of calls</li>
</ul>

<p>The usage for dmtracedump is: </p>

<pre>dmtracedump [-ho] [-s sortable] [-d trace-base-name] [-g outfile] &lt;trace-base-name></pre>

<p>The tool then loads trace log data from &lt;trace-base-name>.data and &lt;trace-base-name>.key. 
	The table below lists the options for dmtracedump.</p>

<table>
<tr>
  <th>Option</td>
  <th>Description</th>
</tr>
  
  <tr>
	<td><code>-d&nbsp;&lt;trace-base-name> </code></td>
	<td>Diff with this trace name</td>
  </tr>
  <tr>
	<td><code>-g&nbsp;&lt;outfile> </code></td>
	<td>Generate output to &lt;outfile></td>
  </tr>
  <tr>
	<td><code>-h </code></td>
	<td>Turn on HTML output</td>
  </tr>
  <tr>
	<td><code>-o </code></td>
	<td>Dump the trace file instead of profiling</td>
  </tr>
  <tr>
	<td><code>-d&nbsp;&lt;trace-base-name> </code></td>
	<td>URL base to the location of the sortable javascript file</td>
  </tr>
  <tr>
	<td><code>-t&nbsp;&lt;percent> </code></td>
	<td>Minimum threshold for including child nodes in the graph (child's inclusive 
		time as a percentage of parent inclusive time). If this option is not used, 
		the default threshold is 20%. </td>
  </tr>

</table>