Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758540AbXFVOmZ (ORCPT ); Fri, 22 Jun 2007 10:42:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756680AbXFVOmS (ORCPT ); Fri, 22 Jun 2007 10:42:18 -0400 Received: from ms-smtp-01.nyroc.rr.com ([24.24.2.55]:46068 "EHLO ms-smtp-01.nyroc.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756516AbXFVOmR (ORCPT ); Fri, 22 Jun 2007 10:42:17 -0400 Subject: Re: [RFC PATCH 0/6] Convert all tasklets to workqueues From: Steven Rostedt To: Arjan van de Ven Cc: LKML , Linus Torvalds , Ingo Molnar , Andrew Morton , Thomas Gleixner , Christoph Hellwig , john stultz , Oleg Nesterov , "Paul E. McKenney" , Dipankar Sarma , "David S. Miller" , matthew.wilcox@hp.com, kuznet@ms2.inr.ac.ru In-Reply-To: <1182522309.2672.11.camel@laptopd505.fenrus.org> References: <20070622040014.234651401@goodmis.org> <1182522309.2672.11.camel@laptopd505.fenrus.org> Content-Type: text/plain Date: Fri, 22 Jun 2007 10:42:10 -0400 Message-Id: <1182523330.5493.69.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1350 Lines: 35 On Fri, 2007-06-22 at 07:25 -0700, Arjan van de Ven wrote: > > The most part, tasklets today are not used for time critical functions. > > Running tasklets in thread context is not harmful to performance of > > the overall system. > > That is a bold statement... > > > But running them in interrupt context is, since > > they increase the overall latency for high priority tasks. > > > .... since by moving this to process context you do add latency between > the hardirq and the tasklet, and I can see that having performance > impact easily. This is stated on the assumption that pretty much all performance critical tasklets have been removed (although Christoph just mentioned megaraid_sas, but after I made this statement). We've been running tasklets as threads in the -rt kernel for some time now, and that hasn't bothered us. The problem with tasklets is that they still don't provide guaranteed performance. They can still be pushed off to ksoftirqd on a busy system. But having *all* tasklets as they are today, keeps them at a higher priority then any process in the system. -- Steve - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/