{namespace buck.performance}

/***/
{template .soyweb}
  {call buck.page}
    {param title: 'Performance Tuning' /}
    {param content}

<h2>Performance Tuning Your Builds</h2>

Buck <a href="{ROOT}concept/what_makes_buck_so_fast.html">does a lot of work</a>
{sp} to make builds as fast as possible, and we also give developers tools to
figure out where the time is being spent inside of their builds.

<h2>Super Console</h2>

<img id="super_console_sample"
     src="{ROOT}static/buck-build-15fps.gif"
     alt="Chrome Tracing Sample">

<p>

When running Buck in an{sp}
<a href="http://en.wikipedia.org/wiki/ANSI_escape_code">Ansi</a> compliant
terminal, Buck displays the break down of
what each thread is doing, updated every 100ms, in what we affectionately call
"SuperConsole."  While a build is running, this gives developers a good idea of
what Buck is spending its time doing, and can often help people spot issues in
their builds.  If you want to see what happened after the fact or to have a
trace you can send around your team, use Chrome Tracing.

<h2>Chrome Tracing</h2>

<img id="chrome_sample"
     src="{ROOT}static/buck_chrome_sample.png"
     alt="Chrome Tracing Sample">

The Chrome team has built an awesome framework for viewing performance traces
right inside of{sp}
<a href="http://www.chromium.org/developers/how-tos/trace-event-profiling-tool">
Chrome</a>.  You can access this by going to <code>chrome://tracing</code> in
your browser.  Consult the trace viewer's
{sp}<a href="https://code.google.com/p/trace-viewer/">project page</a> for more
information on the trace viewer and the file format.

<p>

After Buck is done with each build, it will produce a Chrome Trace file that can
be loaded up in <code>chrome://tracing</code> in the directory
{sp}<code>buck-out/log/traces/</code>.  Buck will save a file in the format
<code>build.[timestamp].trace</code>, and then create a symlink from the most
recent trace to <code>build.trace</code>.

<p>

To load up this trace, visit <code>chrome://tracing</code> inside of Chrome, and
hit "Load".  Load the trace file of interest, and look around to see where time
was spent.  Each row represents a different thread, and all of the steps taken
for a given rule are logged underneath that rule.  Additionally, we log
information about how the rule was built and and the rule key for each artifact
fetch.  Press <em>?</em> to get the help menu for the Chrome Trace Viewer.

    {/param}  // content
  {/call} // buck.page
{/template}