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diff --git a/docs/html/tools/debugging/systrace.jd b/docs/html/tools/debugging/systrace.jd new file mode 100644 index 0000000..287abe6 --- /dev/null +++ b/docs/html/tools/debugging/systrace.jd @@ -0,0 +1,239 @@ +page.title=Analyzing Display and Performance with Systrace +parent.title=Debugging +parent.link=index.html +@jd:body + +<div id="qv-wrapper"> + <div id="qv"> + <h2>In this document</h2> + <ol> + <li><a href="#overview">Overview</a> + </li> + <li><a href="#generate">Generating Traces</a> + <ol> + <li><a href="#limit-trace">Limiting trace data</a></li> + <li><a href="#config-categories">Configuring trace data categories</a></li> + <li><a href="#running">Running a trace</a></li> + </ol> + </li> + <li><a href="#analysis">Analyzing Traces</a> + <ol> + <li><a href="#long-processes">Long running processes</a></li> + <li><a href="#display-interupts">Interruptions in display execution</a></li> + </ol> + </li> + </ol> + <h2>See also</h2> + <ol> + <li><a href="{@docRoot}tools/help/systrace.html">Systrace</a> + </li> + </ol> + </div> +</div> + +<p>After building features, eliminating bugs and cleaning up your code, you should spend some + time looking at the performance of your application. The speed and smoothness with which your + application draws pixels and performs operations has an significant impact on your users' + experience.</p> + +<p>Android applications operate within a shared resource environment, and the performance of + your application can be impacted by how efficiently it interacts with those resources in + the larger system. Applications also operate in a multithreaded environment, competing with other + threaded processes for resources, which can cause performance problems that are hard to diagnose. +</p> + +<p>The {@code systrace} tool allows you to collect and review code execution data for your + application and the Android system. You can use this data to diagnose execution problems and + improve the performance of your application.</p> + + +<h2 id="overview">Overview</h2> + +<p>{@code systrace} helps you analyze how the execution of your application fits into the larger + Android environment, letting you see system and applications process execution on a common + timeline. The tool allows you to generate highly detailed, interactive reports from devices + running Android 4.1 and higher, such as the report in figure 1.</p> + +<img src="{@docRoot}images/systrace/report.png" alt="Systrace example report" id="figure1" /> +<p class="img-caption"> + <strong>Figure 1.</strong> An example {@code systrace} report on 5 seconds of process execution + for a running application and related Android system processes. +</p> + + +<h2 id="generate">Generating Traces</h2> + +<p>In order to create a trace of your application, you must perform a few setup steps. First, you + must have a device running Android 4.1 or higher. Setup the device for + <a href="{@docRoot}tools/device.html#setting-up">debugging</a>, connect it to your development + system and install your application. Some types of trace information, specifically disk activity + and kernel work queues, require root access to the device, but most {@code systrace} log data + only requires that the device be enabled for developer debugging.</p> + + +<h3 id="limit-trace">Limiting trace data</h3> + +<p>The {@code systrace} tool can generate a potentially huge amount of data from applications + and system sources. To limit the amount of data the tool collects and make the data more relevant + to your analysis, use the following options:</p> + +<ul> + <li>Limit the amount of time covered by the trace with the {@code -t, --time} option. The default + length of a trace is 5 seconds.</li> + <li>Limit the size of the data collected by the trace with the {@code -b, --buf-size} option.</li> + <li>Specify what types of processes are traced using the {@code --set-tags} option and the + {@code --disk}, {@code --cpu-freq}, {@code --cpu-idle}, {@code --cpu-load} options.</li> +</ul> + + +<h3 id="config-categories">Configuring trace data categories</h3> + +<p>To use {@code systrace} effectively, you must specify the types of processes you want to trace. + The tool can gather the following types of process information:</p> + +<ul> + <li>General system processes such as graphics, audio and input processes (selected using trace + <a href="{@docRoot}tools/help/systrace.html#tags">Tags</a>).</li> + <li>Low level system information such as CPU, kernel and disk activity (selected using + <a href="{@docRoot}tools/help/systrace.html#options">Options</a>).</li> +</ul> + +<p>To set trace tags for {@code systrace} using the command-line:</p> + +<ol> + <li>Use the {@code --set-tags} option: +<pre> +$> python systrace.py --set-tags=gfx,view,wm +</pre> + </li> + <li>Stop and restart the {@code adb} shell to enable tracing of these processes. +<pre> +$> adb shell stop +$> adb shell start +</pre></li> +</ol> + +<p>To set trace tags for {@code systrace} using the device user interface:</p> + +<ol> + <li>On the device connected for tracing, navigate to: <strong>Settings > + Developer options > Monitoring > Enable traces</strong>.</li> + <li>Select the categories of processes to be traced and click <strong>OK</strong>.</li> +</ol> + +<p class="note"> + <strong>Note:</strong> The {@code adb} shell does not have to be stopped and restarted when + selecting trace tags using this method. +</p> + + +<h3 id="running">Running a trace</h3> + +<p>After you have configured the category tags for your trace, you can start collecting + information for analysis.</p> + +<p>To run a trace using the current trace tag settings:</p> + +<ol> + <li>Make sure the device is connected through a USB cable and is + <a href="{@docRoot}tools/device.html#setting-up">enabled for debugging</a>.</li> + <li>Run the trace with the low-level system trace options and limits you want, for example: +<pre> +$> python systrace.py --cpu-freq --cpu-load --time=10 -o mytracefile.html +</pre> + </li> + <li>On the device, execute any user actions you want be included in the trace.</li> +</ol> + + +<h2 id="analysis">Analyzing Traces</h2> + +<p>After you have generated a trace using {@code systrace}, it lists the location of the output + file and you can open the report using a web browser. + How you use the trace data depends on the performance issues you are investigating. However, + this section provides some general instructions on how to analyze a trace.</p> + +<p>The reports generated by {@code systrace} are interactive, allowing you to zoom into and out of + the process execution details. Use the <em>W</em> key to zoom in, the <em>S</em> + key to zoom out, the <em>A</em> key to pan left and the <em>D</em> key to pan + right. Select a task in timeline using your mouse to get more information about the task. + For more information about the using the keyboard navigation shortcuts and navigation, see the + <a href="{@docRoot}tools/help/systrace.html#viewing-options">Systrace</a> reference + documentation.</p> + +<h3 id="long-processes">Long running processes</h3> + +<p>A well-behaved application executes many small operations quickly and with a regular rhythm, + with individual operations completing within few milliseconds, depending on the device + and the processes being performed, as shown in figure 2:</p> + +<img src="{@docRoot}images/systrace/process-rhythm.png" alt="Systrace exerpt of app processing" +id="figure2" /> +<p class="img-caption"> + <strong>Figure 2.</strong> Excerpt from a trace of a smoothly running application with a regular + execution rhythm. +</p> + +<p>The trace excerpt in figure 2 shows a well-behaved application with + a regular process rhythm (1). The lower section of figure 2 shows a magnified section of + the trace indicated by the dotted outline, which reveals some irregularity in the process + execution. In particular, one of the wider task bars, indicated by (2), is taking slightly + longer (14 milliseconds) than other, similar tasks on this thread, which are averaging between + 9 and 12 milliseconds to complete. This particular task execution length is likely not noticeable + to a user, unless it impacts another process with specific timing, such as a screen update.</p> + +<p>Long running processes show up as thicker than usual execution bars in a trace. These thicker + bars can indicate a problem in your application performance. When they show up in your + trace, zoom in on the process using the + <a href="{@docRoot}tools/help/systrace.html#viewing-options">keyboard navigation</a> shortcuts to + identify the task causing the problem, and click on the task to get more information. You should + also look at other processes running at the same time, looking for a thread in one process that is + being blocked by another process.</p> + + +<h3 id="display-interupts">Interruptions in display execution</h3> + +<p>The {@code systrace} tool is particularly useful in analyzing application display slowness, + or pauses in animations, because it shows you the execution of your application across multiple + system processes. With display execution, drawing screen frames with a regular rhythm is essential + for good performance. Having a regular rhythm for display ensures that animations and motion are + smooth on screen. If an application drops out of this rhythm, the display can become jerky or slow + from the users perspective.</p> + +<p>If you are analyzing an application for this type of problem, examine the + <strong>SurfaceFlinger</strong> process in the {@code systrace} report where your application is + also executing to look for places where it drops out of its regular rhythm.</p> + +<img src="{@docRoot}images/systrace/display-rhythm.png" alt="Systrace exerpt of display processing" +id="figure3" /> +<p class="img-caption"> + <strong>Figure 3.</strong> Excerpt from a trace of an application showing interruptions in + display processing. +</p> + +<p>The trace excerpt in figure 3 shows an section of a trace that indicates an interruption in the + device display. The section of the <strong>SurfaceFlinger</strong> process in top excerpt, + indicated by (1), shows that display frames are being missed. These + dropped frames are potentially causing the display to stutter or halt. Zooming into this problem + area in the lower trace, shows that a memory operation (image buffer dequeuing and allocation) in + the <strong>surfaceflinger</strong> secondary thread is taking a long time (2). This delay + causes the application to miss the display update window, indicated by the dotted + line. As the developer of this application, you should investigate other threads in your + application that may also be trying to allocate memory at the same time or otherwise blocking + memory allocation with another request or task.</p> + +<p>Regular, rhythmic execution of the <strong>SurfaceFlinger</strong> process is essential to smooth + display of screen content, particularly for animations and motion. Interruptions in the regular + execution pattern of this thread is not always an indication of a display problem with your + application. Further testing is required to determine if this is actually a performance problem + from a user perspective. Being able to identify display execution patterns like the example above + can help you detect display problems and build a smooth-running, high-performance application. +</p> + +<p class="note"> + <strong>Note:</strong> When using {@code systrace} to analyze display problems, make sure + you activate the tracing tags for <strong>Graphics</strong> and <strong>Views</strong>. +</p> + +<p>For more information on the command line options and keyboard controls for {@code systrace}, +see the <a href="{@docRoot}tools/help/systrace.html">Systrace</a> reference page.</p>
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