From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265995AbUAVFSp (ORCPT ); Thu, 22 Jan 2004 00:18:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266092AbUAVFSo (ORCPT ); Thu, 22 Jan 2004 00:18:44 -0500 Received: from mail-04.iinet.net.au ([203.59.3.36]:46824 "HELO mail.iinet.net.au") by vger.kernel.org with SMTP id S265995AbUAVFSA (ORCPT ); Thu, 22 Jan 2004 00:18:00 -0500 Message-ID: <400F5CE5.6000602@cyberone.com.au> Date: Thu, 22 Jan 2004 16:17:25 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030827 Debian/1.4-3 X-Accept-Language: en MIME-Version: 1.0 To: Con Kolivas CC: linux kernel mailing list Subject: Re: Deadline for video capture References: <200401221608.05924.kernel@kolivas.org> In-Reply-To: <200401221608.05924.kernel@kolivas.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Con Kolivas wrote: >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > >Hi all > >I suspected that the anticipatory scheduler might not have been the best >choice for video capture because of the interruption to writes by reads and >the subsequent anticipatory delay associated with it. I have now confirmed >that booting with the default anticipatory i/o elevator I get many dropped >frames that I don't get if I boot with elevator=deadline. > >briefly: dual 7200 rpm ATA5 IDE drives in software RAID0 > >I guess there isn't really a lot to do about this, it's a compromise one way >or the other. The anticipatory scheduler seems better all round but in this >large streaming write situation it doesn't seem ideal. Any sysctl settings I >could use to blunt the anticipation just before I do video capture? > echo 0 > /sys/block/*/queue/iosched/antic_expire Turns it off alltogether. You could also adjust read and write batch expire settings which are heavily biased toward reads.