From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264961AbUGSKrL (ORCPT ); Mon, 19 Jul 2004 06:47:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264960AbUGSKrL (ORCPT ); Mon, 19 Jul 2004 06:47:11 -0400 Received: from mx1.elte.hu ([157.181.1.137]:51131 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S264965AbUGSKrH (ORCPT ); Mon, 19 Jul 2004 06:47:07 -0400 Date: Mon, 19 Jul 2004 12:29:54 +0200 From: Ingo Molnar To: Andrew Morton Cc: Lee Revell , 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: <20040719102954.GA5491@elte.hu> References: <20040709182638.GA11310@elte.hu> <20040710222510.0593f4a4.akpm@osdl.org> <1089673014.10777.42.camel@mindpipe> <20040712163141.31ef1ad6.akpm@osdl.org> <1089677823.10777.64.camel@mindpipe> <20040712174639.38c7cf48.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040712174639.38c7cf48.akpm@osdl.org> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton wrote: > > Should I try ext3? > > ext3 is certainly better than that, but still has a couple of > potential problem spots. ext2 is probably the best at this time. with the voluntary-preempt patch applied ext3 is below ~500 usecs for all things i tried on a 2GHz CPU. Without the patch i can trigger latencies up to milliseconds (even with CONFIG_PREEMPT) by triggering a bigger commit stream via some large file write or a cached du / causing a stream of atime updates. (I very much suspect that all other journalled filesystems have similar problems and they'll need measurements and fixing just like ext3 does.) another bigger problem area is the VM - see my patch for details. pagetable zapping and page reclaim are both problematic and need fixups even under CONFIG_PREEMPT. Doing a simple 'make -j' kernel build that hits swap triggers these easily. (after applying my patch the latencies go below 1msec even with a 'make -j' overload.) Ingo