Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266891AbUJFEC6 (ORCPT ); Wed, 6 Oct 2004 00:02:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266888AbUJFEC5 (ORCPT ); Wed, 6 Oct 2004 00:02:57 -0400 Received: from mail-relay-2.tiscali.it ([213.205.33.42]:31460 "EHLO mail-relay-2.tiscali.it") by vger.kernel.org with ESMTP id S266879AbUJFECa (ORCPT ); Wed, 6 Oct 2004 00:02:30 -0400 Date: Wed, 6 Oct 2004 06:03:23 +0200 From: Andrea Arcangeli To: Jeff Garzik Cc: Nick Piggin , Robert Love , Roland Dreier , linux-kernel@vger.kernel.org Subject: Re: Preempt? (was Re: Cannot enable DMA on SATA drive (SCSI-libsata, VIA SATA)) Message-ID: <20041006040323.GL26820@dualathlon.random> References: <52is9or78f.fsf_-_@topspin.com> <4163465F.6070309@pobox.com> <41634A34.20500@yahoo.com.au> <41634CF3.5040807@pobox.com> <1097027575.5062.100.camel@localhost> <20041006015515.GA28536@havoc.gtf.org> <41635248.5090903@yahoo.com.au> <20041006020734.GA29383@havoc.gtf.org> <20041006031726.GK26820@dualathlon.random> <4163660A.4010804@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4163660A.4010804@pobox.com> X-GPG-Key: 1024D/68B9CB43 13D9 8355 295F 4823 7C49 C012 DFA1 686E 68B9 CB43 X-PGP-Key: 1024R/CB4660B9 CC A0 71 81 F4 A0 63 AC C0 4B 81 1D 8C 15 C8 E5 User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 945 Lines: 18 On Tue, Oct 05, 2004 at 11:27:06PM -0400, Jeff Garzik wrote: > You're ignoring the argument :) > > If users and developers are presented with the _impression_ that long > latency code paths don't exist, then nobody is motivated to profile them > (with any tool), much less fix them. well, you are assuming those latencies are visible with eyes. they might be in extreme cases, but normally they're not (what people notices normally are disk latencies, and few people uses an RT userspace anyways which means they cannot claim the problem to be a lack of cond_resched, but more likely they want shorter timeslices in the scheduler etc..). So my point is that you need a measurement tool anyways... - 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/