From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269132AbUIBW1W (ORCPT ); Thu, 2 Sep 2004 18:27:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269152AbUIBWYn (ORCPT ); Thu, 2 Sep 2004 18:24:43 -0400 Received: from fw.osdl.org ([65.172.181.6]:12182 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S268034AbUIBWXI (ORCPT ); Thu, 2 Sep 2004 18:23:08 -0400 Date: Thu, 2 Sep 2004 15:20:46 -0700 From: Andrew Morton To: Andrea Arcangeli Cc: mingo@elte.hu, paul@linuxaudiosystems.com, rlrevell@joe-job.com, linux-audio-dev@music.columbia.edu, arjanv@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch Message-Id: <20040902152046.1b34d793.akpm@osdl.org> In-Reply-To: <20040902220301.GA18212@x30.random> References: <20040713213847.GH974@dualathlon.random> <20040713145424.1217b67f.akpm@osdl.org> <20040713220103.GJ974@dualathlon.random> <20040713152532.6df4a163.akpm@osdl.org> <20040713223701.GM974@dualathlon.random> <20040713154448.4d29e004.akpm@osdl.org> <20040713225305.GO974@dualathlon.random> <20040713160628.596b96a3.akpm@osdl.org> <20040713231803.GP974@dualathlon.random> <20040719115952.GA13564@elte.hu> <20040902220301.GA18212@x30.random> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrea Arcangeli wrote: > > if you're scared that there are too many cond_resched (I'm not scared > and people should enable them anyways if they make a difference, they > still should be less than the number of spin_unlocks with preempt > enabled), then you should add a cond_resched_costly and add a config > option that turns it off. None of these approaches improves worst-case latency at all on SMP. If we're not going to address the SMP problem we could just make it UP-only, in which case increased locking costs are a non-issue. I'd prefer that we find a solution for SMP too though.