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diff --git a/tools/jprof/README.html b/tools/jprof/README.html new file mode 100644 index 0000000000..ac25acc5ef --- /dev/null +++ b/tools/jprof/README.html @@ -0,0 +1,330 @@ +<!-- This Source Code Form is subject to the terms of the Mozilla Public + - License, v. 2.0. If a copy of the MPL was not distributed with this + - file, You can obtain one at http://mozilla.org/MPL/2.0/. --> + +<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><p> +Recent (4/2011) updates Randell Jesup (see bugzilla for contact info) +</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> + +<p>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. On many architectures with GCC, you'll need to add +<code>--enable-optimize="-O3 -fno-omit-frame-pointer"</code> or the +equivalent to ensure frame pointer generation in the compiler you're using.</p> + +<p>Finally, build mozilla with your new configuration. Now you can run jprof.</p> + +<h3><a name="usage">Usage</a></h3> +<pre> jprof [-v] [-t] [-e exclude] [-i include] [-s stackdepth] [--last] [--all] [--start n [--end m]] [--output-dir dir] prog log [log2 ...]</pre> +Options: +<ul> + <li><b>-s depth</b> : Limit depth looked at from captured stack + frames</li> + <li><b>-v</b> : Output some information about the symbols, memory map, etc.</li> + <li><b>-t or --threads</b> : Group output according to thread. May require external + LD_PRELOAD library to help force sampling of spawned threads; jprof + may capture the main thread only. See <a + href="http://sam.zoy.org/writings/programming/gprof.html">gprof-helper</a>; + it may need adaption for jprof.</li> + <li><b>--only-thread id</b> : Only output data for thread 'id'</li> + <li><b>-e exclusion</b> : Allows excluding specific stack frames</li> + <li><b>-i inclusion</b> : Allows including specific stack frames</li> + <li><b>--last</b> : Only process data from the last 'section' of sampling + (starting at the last PROF)</li> + <li><b>--start N</b> : Start processing data at 'section' N </li> + <li><b>--end N</b> : Stop processing data at 'section' N </li> + <li><b>--output-dir dir</b> : Store generated .html files in the given directory </li> +</ul> +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 greater than or equal to 0.001 are supported. Default is + 0.050 (50ms). + + <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. + + <li> <b>JP_CIRCULAR=size</b> : This tells jprof to store samples in a + circular buffer of the given size, which then will be saved (appended) + to disk when SIGUSR1 is received or JProfStopProfiling is done. If the + buffer overflows, the oldest entries will be evicted until there's + space for the new entry.<p> + + SIGUSR2 will cause the circular buffer to be cleared. + + <li> <b>JP_FILENAME=basefilename</b> : This is the filename used for + saving the log files to; the default is "jprof-log". If Electrolysis + is used, each process after the first will have the process ID + added ("jprof-log-3212"); + +</ul> + +<h4>Starting and stopping jprof from JavaScript</h4> +<p> +A build with jprof enabled adds four functions to the Window object:<p> +<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><p> +<code>JProfClearCircular()</code> and <code>JProfSaveCircular()</code>: +These clear the circular buffer and save the buffer (without stopping), respectively.</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 millisecond of + program time use: + <pre> + setenv JPROF_FLAGS "JP_DEFER JP_PERIOD=0.001" </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> + + <li>To make the timer start on JProfStartProfiling() and run continously + with a 1ms sample rate until told to stop, then save the last 1MB of + data: + <pre> + setenv JPROF_FLAGS "JP_DEFER JP_CIRCULAR=1048576 JP_PERIOD=0.001" </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. + +<P>SIGUSR2 will cause the circular buffer to be cleared, if it's in use. +This is useful right before running a test when you're using a large, +continuous circular buffer, or programmatically at the start of an action +which might take too long (JProfClearCircular()). + +<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/objdir/dist/bin/firefox ./jprof-log > tmp.html +</pre> + +This will generate the file <code>tmp.html</code> which you should view in a +web browser. + +<pre> + ./jprof --output-dir=/tmp /home/user/mozilla/objdir/dist/bin/firefox ./jprof-log* +</pre> + +This will generate a set of files in /tmp for each process. + + +<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 ComputedStyle::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 ComputedStyle::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> + index Count Hits Function Name + <A href="#72871"> 545 (46.4%) nsBlockFrame::ReflowInlineFrames(nsBlockReflowState&, nsLineList_iterator, int*)</A> + <A href="#72873"> 100 (8.5%) nsBlockFrame::ReflowDirtyLines(nsBlockReflowState&)</A> + 72870 4 (0.3%) <a name=72870> 645 (54.9%)</a> <b>nsBlockFrame::DoReflowInlineFrames(nsBlockReflowState&, nsLineLayout&, nsLineList_iterator, nsFlowAreaRect&, int&, nsFloatManager::SavedState*, int*, LineReflowStatus*, int)</b> + <A href="#72821"> 545 (46.4%) nsBlockFrame::ReflowInlineFrame(nsBlockReflowState&, nsLineLayout&, nsLineList_iterator, nsIFrame*, LineReflowStatus*)</A> + <A href="#72853"> 83 (7.1%) nsBlockFrame::PlaceLine(nsBlockReflowState&, nsLineLayout&, nsLineList_iterator, nsFloatManager::SavedState*, nsRect&, int&, int*)</A> + <A href="#74150"> 9 (0.8%) nsLineLayout::BeginLineReflow(int, int, int, int, int, int)</A> + <A href="#74897"> 1 (0.1%) nsTextFrame::GetType() const</A> + <A href="#74131"> 1 (0.1%) nsLineLayout::RelativePositionFrames(nsOverflowAreas&)</A> + <A href="#58320"> 1 (0.1%) __i686.get_pc_thunk.bx</A> + <A href="#53077"> 1 (0.1%) PL_ArenaAllocate</A> +</pre></blockquote> + +The information this block tells us is: + +<ul> +<li>There were 4 profiler hits <em>in</em> <code>nsBlockFrame::DoReflowInlineFrames</code> +<li>There were 645 profiler hits <em>in or under</em> <code>nsBlockFrame::DoReflowInlineFrames</code>. Of these: +<ul> + <li>545 were in or under <code>nsBlockFrame::ReflowInlineFrame</code> + <li>83 were in or under <code>nsBlockFrame::PlaceLine</code> + <li>9 were in or under <code>nsLineLayout::BeginLineReflow</code> + <li>1 was in or under <code>nsTextFrame::GetType</code> + <li>1 was in or under <code>nsLineLayout::RelativePositionFrames</code> + <li>1 was in or under <code>__i686.get_pc_thunk.bx</code> + <li>1 was in or under <code>PL_ArenaAllocate</code> +</ul> +<li>Of these 645 calls into <code>nsBlockFrame::DoReflowInlineFrames</code>: +<ul> + <li>545 came from <code>nsBlockFrame::ReflowInlineFrames</code> + <li>100 came from <code>nsBlockFrame::ReflowDirtyLines</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>nsBlockFrame::DoReflowInlineFrames</code>, which is +therefore bolded and not a link. The name of this function is preceded by +five numbers which have the following meaning. The number on the left (72870) +is the index number, and is not important. The next number (4) and the +percentage following (0.3%) are the number +of times this function was interrupted by the timer and the percentage of +the total hits that is. The last number pair ("645 (54.9%)") +are 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>nsBlockFrame::DoReflowInlineFrames</code>. +<p>For our example we can see that our function was in the call stack for +645 interrupt ticks, but we were only the function that was running when +the interrupt arrived 4 times. +<P> +The functions listed above the line for <code>nsBlockFrame::DoReflowInlineFrames</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>nsBlockFrame::DoReflowInlineFrames</code>. In our example, we were called 545 times by +<code>nsBlockFrame::ReflowInlineFrames</code> and 100 times by +<code>nsBlockFrame::ReflowDirtyLines</code>. +<P> +The functions listed below the line for <code>nsBlockFrame::DoReflowInlineFrames</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>nsBlockFrame::DoReflowInlineFrames</code> and the corresponding percentages. In our example, of the 645 profiler hits under <code>nsBlockFrame::DoReflowInlineFrames</code> 545 were under <code>nsBlockFrame::ReflowInlineFrame</code>, 83 were under <code>nsBlockFrame::PlaceLine</code>, and so forth.<p> + +<b>NOTE:</b> If there are loops of execution or recursion, the numbers will +not add up and percentages can exceed 100%. If a function directly calls +itself "(self)" will be appended to the line, but indirect recursion will +not be marked. + +<h3>Bugs</h3> +The current build of Jprof has only been tested under Ubuntu 8.04 LTS, but +should work under any fairly modern linux distribution using GCC/GLIBC. +Please update this document with any known compatibilities/incompatibilities. +<p> +If you get an error:<p><code>Inconsistency detected by ld.so: dl-open.c: 260: dl_open_worker: Assertion `_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT' failed! +</code><p>that means you've hit a timing hole in the version of glibc you're +running. See <a +href="http://sources.redhat.com/bugzilla/show_bug.cgi?id=4578">Redhat bug 4578</a>. +<!-- <h3>Update</h3> +<ul> +</ul> +--> + +</body> +</html> |