mirror of
https://gitlab.winehq.org/wine/wine-gecko.git
synced 2024-09-13 09:24:08 -07:00
271 lines
12 KiB
HTML
271 lines
12 KiB
HTML
<html>
|
|
<head><title>The Jprof Profiler</title></head>
|
|
|
|
<body bgcolor="#FFFFFF" text="#000000"
|
|
link="#0000EE" vlink="#551A8B" alink="#FF0000">
|
|
<center>
|
|
<h1>The Jprof Profiler</h1>
|
|
<font size="-1">
|
|
<a href="mailto:jim_nance%yahoo.com">jim_nance@yahoo.com</a>
|
|
</font>
|
|
<hr>
|
|
|
|
<a href="#introduction">Introduction</a> | <a href="#operation">Operation</a> |
|
|
<a href="#setup">Setup</a> | <a href="#usage">Usage</a> |
|
|
<a href="#interpretation">Interpretation</a>
|
|
|
|
</center>
|
|
<hr>
|
|
|
|
<h3><a name="introduction">Introduction</a></h3>
|
|
|
|
Jprof is a profiling tool. I am writing it because I need to find out
|
|
where mozilla is spending its time, and there do not seem to be any
|
|
profilers for Linux that can handle threads and/or shared libraries.
|
|
This code is based heavily on Kipp Hickman's leaky.
|
|
|
|
<h3><a name="operation">Operation</a></h3>
|
|
|
|
Jprof operates by installing a timer which periodically interrupts mozilla.
|
|
When this timer goes off, the jprof code inside mozilla walks the function call
|
|
stack to determine which code was executing and saves the results into the
|
|
<code>jprof-log</code> and <code>jprof-map</code> files. By collecting a large
|
|
number of these call stacks, it is possible to deduce where mozilla is spending
|
|
its time.
|
|
|
|
<h3><a name="setup">Setup</a></h3>
|
|
|
|
First, check out the jprof source code since it is not a part of the
|
|
default pull. To do this do:
|
|
<pre>
|
|
cvs co mozilla/tools/jprof
|
|
</pre>
|
|
|
|
<p>Next, configure your mozilla with jprof support by adding
|
|
<code>--enable-jprof</code> to your configure options (eg adding
|
|
<code>ac_add_options --enable-jprof</code> to your <code>.mozconfig</code>) and
|
|
making sure that you do <strong>not</strong> have the
|
|
<code>--enable-strip</code> configure option set -- jprof needs symbols to
|
|
operate.</p>
|
|
|
|
<p>Finally, build mozilla with your new configuration. Now you can run jprof.</p>
|
|
|
|
<h3><a name="usage">Usage</a></h3>
|
|
|
|
The behavior of jprof is determined by the value of the JPROF_FLAGS environment
|
|
variable. This environment variable can be composed of several substrings
|
|
which have the following meanings:
|
|
<ul>
|
|
<li> <b>JP_START</b> : Install the signal handler, and start sending the
|
|
timer signals.
|
|
|
|
<li> <b>JP_DEFER</b> : Install the signal handler, but don't start sending
|
|
the timer signals. The user must start the signals by sending the first
|
|
one (with <code>kill -PROF</code>, or with <code>kill -ALRM</code> if
|
|
JP_REALTIME is used, or with <code>kill -POLL</code> (also known as <code>kill -IO</code>) if JP_RTC_HZ is used).
|
|
|
|
<li> <b>JP_FIRST=x</b> : Wait x seconds before starting the timer
|
|
|
|
<li> <b>JP_PERIOD=y</b> : Set timer to interrupt every y seconds. Only
|
|
values of y strictly greater than 0.001 are supported.
|
|
|
|
<li> <b>JP_REALTIME</b> : Do the profiling in intervals of real time rather
|
|
than intervals of time used by the mozilla process (and the kernel
|
|
when doing work for mozilla). This could probably lead to weird
|
|
results (you'll see whatever runs when mozilla is waiting for events),
|
|
but is needed to see time spent in the X server.
|
|
|
|
<li> <b>JP_RTC_HZ=freq</b> : This option, only available on Linux if the
|
|
kernel is built with RTC support, makes jprof use the RTC timer instead of
|
|
using its own timer. This option, like JP_REALTIME, uses intervals of real
|
|
time. This option overrides JP_PERIOD. <code>freq</code> is the frequency
|
|
at which the timer should fire, measured in Hz. It must be a power of 2.
|
|
The maximal frequency allowed by the kernel can be changed by writing to
|
|
<code>/proc/sys/dev/rtc/max-user-freq</code>; the maximum value it can be
|
|
set to is 8192. Note that <code>/dev/rtc</code> will need to be readable
|
|
by the Firefox process; making that file world-readable is a simple way to
|
|
accomplish that.
|
|
</ul>
|
|
|
|
<h4>Starting and stopping jprof from JavaScript</h4>
|
|
<p>
|
|
A build with jprof enabled adds two functions to the Window object:
|
|
<code>JProfStartProfiling()</code> and <code>JProfStopProfiling()</code>. When used with JP_DEFER, these
|
|
allow one to start and stop the timer just around whatever critical section is
|
|
being profiled
|
|
</p>
|
|
|
|
<h4>Examples of JPROF_FLAGS usage</h4>
|
|
<ul>
|
|
|
|
<li>To make the timer start firing 3 seconds after the program is started and
|
|
fire every 25 milliseconds of program time use:
|
|
<pre>
|
|
setenv JPROF_FLAGS "JP_START JP_FIRST=3 JP_PERIOD=0.025" </pre>
|
|
|
|
<li>To make the timer start on your signal and fire every 1.5 milliseconds of
|
|
program time use:
|
|
<pre>
|
|
setenv JPROF_FLAGS "JP_DEFER JP_PERIOD=0.0015" </pre>
|
|
|
|
<li>To make the timer start on your signal and fire every 10 milliseconds of
|
|
wall-clock time use:
|
|
<pre>
|
|
setenv JPROF_FLAGS "JP_DEFER JP_PERIOD=0.010 JP_REALTIME" </pre>
|
|
|
|
<li>To make the timer start on your signal and fire at 8192 Hz in wall-clock
|
|
time use:
|
|
<pre>
|
|
setenv JPROF_FLAGS "JP_DEFER JP_RTC_HZ=8192" </pre>
|
|
|
|
</ul>
|
|
|
|
<h4>Pausing profiles</h4>
|
|
|
|
<P>jprof can be paused at any time by sending a SIGUSR1 to mozilla (<code>kill
|
|
-USR1</code>). This will cause the timer signals to stop and jprof-map to be
|
|
written, but it will not close jprof-log. Combining SIGUSR1 with the JP_DEFER
|
|
option allows profiling of one sequence of actions by starting the timer right
|
|
before starting the actions and stopping the timer right afterward.
|
|
|
|
<P>After a SIGUSR1, sending another timer signal (SIGPROF, SIGALRM, or SIGPOLL (aka SIGIO),
|
|
depending on the mode) can be used to continue writing data to the same output.
|
|
|
|
<h4>Looking at the results</h4>
|
|
|
|
Now that we have <code>jprof-log</code> and <code>jprof-map</code> files, we
|
|
can use the jprof executable is used to turn them into readable output. To do
|
|
this jprof needs the name of the mozilla binary and the log file. It deduces
|
|
the name of the map file:
|
|
|
|
<pre>
|
|
./jprof /home/user/mozilla/debug/dist/bin/mozilla-bin ./jprof-log > tmp.html
|
|
</pre>
|
|
|
|
This will generate the file <code>tmp.html</code> which you should view in a
|
|
web browser.
|
|
|
|
<h3><a name="interpretation">Interpretation</a></h3>
|
|
|
|
|
|
The Jprof output is split into a flat portion and a hierarchical portion.
|
|
There are links to each section at the top of the page. It is typically
|
|
easier to analyze the profile by starting with the flat output and following
|
|
the links contained in the flat output up to the hierarchical output.
|
|
|
|
<h4><a name="flat">Flat output</a></h3>
|
|
|
|
The flat portion of the profile indicates which functions were executing
|
|
when the timer was going off. It is displayed as a list of functions names
|
|
on the right and the number of times that function was interrupted on the
|
|
left. The list is sorted by decreasing interrupt count. For example:
|
|
|
|
<blockquote> <pre>
|
|
Total hit count: 151603
|
|
Count %Total Function Name
|
|
|
|
<a href="#23081">8806 5.8 __libc_poll</a>
|
|
<a href="#40008">2254 1.5 __i686.get_pc_thunk.bx</a>
|
|
<a href="#21390">2053 1.4 _int_malloc</a>
|
|
<a href="#49013">1777 1.2 nsStyleContext::GetStyleData(nsStyleStructID)</a>
|
|
<a href="#21380">1600 1.1 __libc_malloc</a>
|
|
<a href="#603">1552 1.0 nsCOMPtr_base::~nsCOMPtr_base()</a>
|
|
</pre> </blockquote>
|
|
|
|
This shows that of the 151603 times the timer fired, 1777 (1.2% of the total) were inside nsStyleContext::GetStyleData() and 1552 (1.0% of the total) were in the nsCOMPtr_base destructor.
|
|
|
|
<p>
|
|
In general, the functions with the highest count are the functions which
|
|
are taking the most time.
|
|
|
|
<P>
|
|
The function names are linked to the entry for that function in the
|
|
hierarchical profile, which is described in the next section.
|
|
|
|
<h4><a name="hier">Hierarchical output</a></h4>
|
|
|
|
The hierarchical output is divided up into sections, with each section
|
|
corresponding to one function. A typical section looks something like
|
|
this:
|
|
|
|
<blockquote><pre>
|
|
<A href="#29355">141300 PL_ProcessPendingEvents</A>
|
|
<A href="#29372"> 927 PL_ProcessEventsBeforeID</A>
|
|
29358 0 <a name=29358> 142227</a> <b>PL_HandleEvent</b>
|
|
<A href="#28546"> 92394 nsInputStreamReadyEvent::EventHandler(PLEvent*)</A>
|
|
<A href="#41572"> 49181 HandlePLEvent(ReflowEvent*)</A>
|
|
<A href="#29537"> 481 handleTimerEvent(TimerEventType*)</A>
|
|
<A href="#34494"> 158 nsTransportStatusEvent::HandleEvent(PLEvent*)</A>
|
|
<A href="#29359"> 9 PL_DestroyEvent</A>
|
|
|
|
<A href="#20319"> 4 __restore_rt</A>
|
|
</pre></blockquote>
|
|
|
|
The information this block tells us is:
|
|
|
|
<ul>
|
|
<li>There were 0 profiler hits <em>in</em> <code>PL_HandleEvent</code>
|
|
<li>There were 142227 profiler hits <em>under</em> <code>PL_HandleEvent</code>. Of these:
|
|
<ul>
|
|
<li>92394 were in or under <code>nsInputStreamReadyEvent::EventHandler</code>
|
|
<li>49181 were in or under <code>HandlePLEvent(ReflowEvent*)</code>
|
|
<li>481 were in or under <code>handleTimerEvent</code>
|
|
<li>158 were in or under <code>nsTransportStatusEvent::HandleEvent</code>
|
|
<li>9 were in or under <code>PL_DestroyEvent</code>
|
|
<li>4 were in or under <code>__restore_rt</code>
|
|
</ul>
|
|
<li>Of these 142227 calls into <code>PL_HandleEvent</code>:
|
|
<ul>
|
|
<li>141300 came from <code>PL_ProcessPendingEvents</code>
|
|
<li>927 came from <code>PL_ProcessEventsBeforeID</code>
|
|
</ul>
|
|
</ul>
|
|
|
|
|
|
The rest of this section explains how to read this information off from the jprof output.
|
|
|
|
<p>This block corresponds to the function <code>PL_HandleEvent</code>, which is
|
|
therefore bolded and not a link. The name of this function is preceded by
|
|
three numbers which have the following meaning. The number on the left (29358)
|
|
is the index number, and is not important. The center number (0) is the number
|
|
of times this function was interrupted by the timer. The last number (142227)
|
|
is the number of times this function was in the call stack when the timer went
|
|
off. That is, the timer went off while we were in code that was ultimately
|
|
called from <code>PL_HandleEvent</code>.
|
|
<p>For our example we can see that our function was in the call stack for
|
|
142227 interrupt ticks, but we were never the function that was running when
|
|
the interrupt arrived.
|
|
<P>
|
|
The functions listed above the line for <code>PL_HandleEvent</code> are its
|
|
callers. The numbers to the left of these function names are the numbers of
|
|
times these functions were in the call stack as callers of
|
|
<code>PL_HandleEvent</code>. In our example, we were called 927 times by
|
|
<code>PL_ProcessEventsBeforeID</code> and 141300 times by
|
|
<code>PL_ProcessPendingEvents</code>.
|
|
<P>
|
|
The functions listed below the line for <code>PL_HandleEvent</code> are its
|
|
callees. The numbers to the left of the function names are the numbers of
|
|
times these functions were in the callstack as callees of <code>PL_HandleEvent</code>. In our example, of the 142227 profiler hits under <code>PL_HandleEvent</code> 92394 were under <code>nsInputStreamReadyEvent::EventHandler</code>, 49181 were under <code>HandlePLEvent(ReflowEvent*)</code>, and so forth.
|
|
|
|
<h3>Bugs</h3>
|
|
Jprof has only been tested under Red Hat Linux 6.0, 6.1, and 6.2. It does
|
|
not work under 6.0, though it is possible hack up the source code and make
|
|
it work there. The way I determine the stack trace from inside the
|
|
signal handler is tightly bound to the version of glibc that is running.
|
|
If you know of a more portable way to get this information please let
|
|
me know.
|
|
|
|
<h3>Update</h3>
|
|
<ul>
|
|
<li>Ben Bucksch reports that installing the Red Hat 6.1 glibc rpms on a Red Hat
|
|
6.0 system allows jprof to work, and does not seem to break anything except
|
|
gdm (the Gnome login program), and that can be fixed by installing the RH 6.1
|
|
gdb rpm.</li>
|
|
<li>David Baron reports that jprof works under RedHat 6.0 if one uncomments
|
|
the <code>#define JPROF_PTHREAD_HACK</code> near the beginning of
|
|
<code>libmalloc.cpp</code>.</li>
|
|
</ul>
|
|
|
|
</body>
|
|
</html>
|