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 15:26:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 18 May 2001 15:26:05 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:27404 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id ; Fri, 18 May 2001 15:25:51 -0400 Date: Fri, 18 May 2001 21:25:31 +0200 From: Jens Axboe To: Eduard Hasenleithner , linux-kernel@vger.kernel.org Subject: Re: DVD blockdevice buffers Message-ID: <20010518212531.A6763@suse.de> In-Reply-To: <20010518210226.A7147@moserv.hasi> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20010518210226.A7147@moserv.hasi>; from eduardh@aon.at on Fri, May 18, 2001 at 09:02:26PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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* -- Jens Axboe