From mboxrd@z Thu Jan 1 00:00:00 1970 From: Armin Steinhoff Subject: Re: Question regarding pthread_cond_wait/pthread_cond_signal latencies Date: Sun, 22 May 2011 16:53:17 +0200 Message-ID: <4DD9235D.50900@steinhoff.de> References: <1305890110.10494.32.camel@laika> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-rt-users To: Pedro Gonnet Return-path: Received: from moutng.kundenserver.de ([212.227.17.9]:49795 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755018Ab1EVOpa (ORCPT ); Sun, 22 May 2011 10:45:30 -0400 In-Reply-To: <1305890110.10494.32.camel@laika> Sender: linux-rt-users-owner@vger.kernel.org List-ID: 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) 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 > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >