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<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>1996</year><year>2009</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>eprof</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
</header>
<module>eprof</module>
<modulesummary>A Time Profiling Tool for Erlang</modulesummary>
<description>
<p>The module <c>eprof</c> provides a set of functions for time
profiling of Erlang programs to find out how the execution time is
used. The profiling is done using the Erlang trace BIFs. Tracing of
local function calls for a specified set of processes is enabled when
profiling is begun, and disabled when profiling is stopped.</p>
<p>When using Eprof, expect a significant slowdown in program execution,
in most cases at least 100 percent.</p>
</description>
<funcs>
<func>
<name>start() -> {ok,Pid} | {error,Reason}</name>
<fsummary>Start Eprof.</fsummary>
<type>
<v>Pid = pid()</v>
<v>Reason = {already_started,Pid}</v>
</type>
<desc>
<p>Starts the Eprof server which owns the Eprof internal database.</p>
</desc>
</func>
<func>
<name>start_profiling(Rootset) -> profiling | error</name>
<name>profile(Rootset) -> profiling | error</name>
<fsummary>Start profiling.</fsummary>
<type>
<v>Rootset = [atom() | pid()]</v>
</type>
<desc>
<p>Starts profiling for the processes in <c>Rootset</c> (and any new
processes spawned from them). Information about activity in any
profiled process is stored in the Eprof database.</p>
<p><c>Rootset</c> is a list of pids and registered names.</p>
<p>The function returns <c>profiling</c> if tracing could be enabled
for all processes in <c>Rootset</c>, or <c>error</c> otherwise.</p>
</desc>
</func>
<func>
<name>stop_profiling() -> profiling_stopped | profiling_already_stopped</name>
<fsummary>Stop profiling.</fsummary>
<desc>
<p>Stops profiling started with <c>start_profiling/1</c> or
<c>profile/1</c>.</p>
</desc>
</func>
<func>
<name>profile(Rootset,Fun) -> {ok,Value} | {error,Reason} | error</name>
<name>profile(Rootset,Module,Function,Args) -> {ok,Value} | {error,Reason} | error</name>
<fsummary>Start profiling.</fsummary>
<type>
<v>Rootset = [atom() | pid()]</v>
<v>Fun = fun() -> term()</v>
<v>Module = Function = atom()</v>
<v>Args = [term()]</v>
<v>Value = Reason = term()</v>
</type>
<desc>
<p>This function first spawns a process <c>P</c> which evaluates
<c>Fun()</c> or <c>apply(Module,Function,Args)</c>. Then, it
starts profiling for <c>P</c> and the processes in <c>Rootset</c>
(and any new processes spawned from them). Information about
activity in any profiled process is stored in the Eprof database.</p>
<p><c>Rootset</c> is a list of pids and registered names.</p>
<p>If tracing could be enabled for <c>P</c> and all processes in
<c>Rootset</c>, the function returns <c>{ok,Value}</c> when
<c>Fun()</c>/<c>apply</c> returns with the value <c>Value</c>, or
<c>{error,Reason}</c> if <c>Fun()</c>/<c>apply</c> fails with
exit reason <c>Reason</c>. Otherwise it returns <c>error</c>
immediately.</p>
<p>The programmer must ensure that the function given as argument
is truly synchronous and that no work continues after
the function has returned a value.</p>
</desc>
</func>
<func>
<name>analyse()</name>
<fsummary>Display profiling results per process.</fsummary>
<desc>
<p>Call this function when profiling has been stopped to display
the results per process, that is:</p>
<list type="bulleted">
<item>how much time has been used by each process, and</item>
<item>in which function calls this time has been spent.</item>
</list>
<p>Time is shown as percentage of total time, not as absolute time.</p>
</desc>
</func>
<func>
<name>total_analyse()</name>
<fsummary>Display profiling results per function call.</fsummary>
<desc>
<p>Call this function when profiling has been stopped to display
the results per function call, that is in which function calls
the time has been spent.</p>
<p>Time is shown as percentage of total time, not as absolute time.</p>
</desc>
</func>
<func>
<name>log(File) -> ok</name>
<fsummary>Activate logging of <c>eprof</c>printouts.</fsummary>
<type>
<v>File = atom() | string()</v>
</type>
<desc>
<p>This function ensures that the results displayed by
<c>analyse/0</c> and <c>total_analyse/0</c> are printed both to
the file <c>File</c> and the screen.</p>
</desc>
</func>
<func>
<name>stop() -> stopped</name>
<fsummary>Stop Eprof.</fsummary>
<desc>
<p>Stops the Eprof server.</p>
</desc>
</func>
</funcs>
</erlref>
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