Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S270329AbUJUMAl (ORCPT ); Thu, 21 Oct 2004 08:00:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268723AbUJTRWV (ORCPT ); Wed, 20 Oct 2004 13:22:21 -0400 Received: from viper.oldcity.dca.net ([216.158.38.4]:47767 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S268719AbUJTRPV (ORCPT ); Wed, 20 Oct 2004 13:15:21 -0400 Subject: Re: [PATCH 1/3] Separate IRQ-stacks from 4K-stacks option From: Lee Revell To: Andrea Arcangeli Cc: Arjan van de Ven , Timothy Miller , Hugh Dickins , "Martin J. Bligh" , Andrea Arcangeli , Alan Cox , Chris Wedgwood , LKML , Christoph Hellwig In-Reply-To: <20041020170802.GB24619@dualathlon.random> References: <593560000.1094826651@[10.10.2.4]> <20040910151538.GA24434@devserv.devel.redhat.com> <20040910152852.GC15643@x30.random> <20040910153421.GD24434@devserv.devel.redhat.com> <41768858.8070709@techsource.com> <20041020153521.GB21556@devserv.devel.redhat.com> <1098290345.1429.65.camel@krustophenia.net> <20041020165050.GA24619@dualathlon.random> <1098291315.1429.79.camel@krustophenia.net> <20041020170802.GB24619@dualathlon.random> Content-Type: text/plain Message-Id: <1098292516.1429.116.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Wed, 20 Oct 2004 13:15:16 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1364 Lines: 30 On Wed, 2004-10-20 at 13:08, Andrea Arcangeli wrote: > On Wed, Oct 20, 2004 at 12:55:17PM -0400, Lee Revell wrote: > > This was not my point, I agree that the two have nothing to do with each > > other. But if a hardirq handler runs for 3ms then no user code can run > > for 3ms. Therefore this is a problem if our goal for desktop response > > is 1ms. > > I sure agree it's a problem, but not always userspace code needs to run > for the user not to notice. With ring buffers in the kernel for playback > all you need is a nested irq for the user not to notice skips. > I was thinking of X, not audio. This might be a problem for AV playback. Maybe that would depend on if DRI was in use. Anyway I use a low latency kernel because i need sub-ms response, I was just pointing out that the current behavior might not be compatible with the 1ms target. However with the patch in -mm that enables setting max_sectors_kb, the 1ms goal can be achived by lowering this to 256 or so. If I were shipping a desktop distro I would lower this by default. My tests show the slowdown is barely measurable if at all. Lee - 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/