From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 18 May 2001 16:01:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 18 May 2001 16:01:15 -0400 Received: from WARSL401PIP1.highway.telekom.at ([195.3.96.69]:56600 "HELO email01.aon.at") by vger.kernel.org with SMTP id ; Fri, 18 May 2001 16:01:10 -0400 Date: Fri, 18 May 2001 21:59:52 +0200 From: Eduard Hasenleithner To: linux-kernel@vger.kernel.org Subject: Re: DVD blockdevice buffers Message-ID: <20010518215952.A7919@moserv.hasi> Mail-Followup-To: Eduard Hasenleithner , linux-kernel@vger.kernel.org In-Reply-To: <20010518210226.A7147@moserv.hasi> <20010518212531.A6763@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.12i In-Reply-To: <20010518212531.A6763@suse.de>; from axboe@suse.de on Fri, May 18, 2001 at 09:25:31PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 18, 2001 at 09:25:31PM +0200, Jens Axboe wrote: > On Fri, May 18 2001, Eduard Hasenleithner wrote: > > I have a problem with the buffering mechanism of my blockdevice, > > namely a ide_scsi DVD-ROM drive. After inserting a DVD and reading > > data linearly from the DVD, an excessive amount of buffer memory gets > > allocated. > > > > This can easily be reproduced with > > cat /dev/sr0 > /dev/null > > > > Remember, nearly the same task is carried out when playing a DVD. > > > > As a result the system performance goes down. I'm still able to use > > my applications, but es every single piece of unused memory is swapped > > out, and swapping in costs a certain amount of time. > > That's why streaming media applications like a dvd player should use raw > I/O -- to bypass system cache. See /dev/raw* > Oh, thank you. That was very fast! I use xine. To be honest, the procedure of how to create a raw device is described in their FAQ. But it is not described, what the raw device does, only that it provides a speed improvement. Until today, I didn't know what rawio actually does. Strange that I didn't come across on some information about it. Was there a official announcement of the availability of this feature? Is some more detailled information about the rawio existing? -- Eduard Hasenleithner student of Salzburg University of Applied Sciences and Technologies