From: Armin Steinhoff <armin@steinhoff.de>
To: Pedro Gonnet <gonnet@maths.ox.ac.uk>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Subject: Re: Question regarding pthread_cond_wait/pthread_cond_signal latencies
Date: Sun, 22 May 2011 17:18:33 +0200 [thread overview]
Message-ID: <4DD92949.4010401@steinhoff.de> (raw)
In-Reply-To: <4DD9235D.50900@steinhoff.de>
Armin Steinhoff wrote:
> Pedro Gonnet wrote:
>> Hi guys,
>>
>> I'm currently working on a shared-memory parallel Molecular Dynamics
>> simulation library (http://mdcore.sourceforge.net/) geared towards
>> multi-core systems.
>>
>> The library uses pthreads (plus some OpenMP for some simple loops) and
>> uses pthread_cond_wait and pthread_cond_signal to coordinate a group of
>> worker threads.
>>
>> I've been profiling the library on different machines and kernels and
>> have noticed that in many cases there are significant (several ms,
>> measured with Intel's Vtune-thing) lags between calls to
>> pthread_cond_signal and the waiting thread actually getting back to
>> work.
>
> At what priority are the worker threads running ?
>
> In order to schedule these threads by the real-time part of the CFS
> scheduler they should run at lest at a priority of 20 (rt_sched_class)
... and you have to use SCHED_RR or SCHED_FIFO for the scheduling
method
--Armin
>
> Regards
>
> --Armin
>
>
>> I've tried the Ubuntu -rt and -preempt kernels, and the whole simulation
>> runs twice as slowly, despite following the advice given here:
>>
>>
>> https://rt.wiki.kernel.org/index.php/HOWTO:_Build_an_RT-application
>>
>> My question is the following: which kernel (or set of configuration
>> options) will minimize these latencies? And if linux-rt is the answer,
>> in what ways do I have to be careful when porting the simulation for
>> this kernel?
>>
>> Cheers and thanks,
>> Pedro
>>
>>
>>
>>
>> --
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>
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next prev parent reply other threads:[~2011-05-22 15:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-20 11:15 Question regarding pthread_cond_wait/pthread_cond_signal latencies Pedro Gonnet
2011-05-22 14:53 ` Armin Steinhoff
2011-05-22 15:18 ` Armin Steinhoff [this message]
-- strict thread matches above, loose matches on Subject: below --
2011-05-20 10:08 Pedro Gonnet
2011-05-21 20:48 ` Mark Hounschell
2011-05-21 20:51 ` Pedro Gonnet
2011-05-21 21:40 ` Rolando Martins
2011-05-22 0:44 ` Peter W. Morreale
2011-05-22 11:34 ` Pedro Gonnet
2011-05-22 13:51 ` Peter W. Morreale
2011-05-22 18:37 ` Robert Schwebel
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