From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <4BE1245F.801@msgid.tls.msk.ru> Date: Wed, 05 May 2010 11:55:11 +0400 From: Michael Tokarev MIME-Version: 1.0 Subject: Re: deadline ALWAYS default for dasd devices(s390) ? References: <4BD58848.8090205@gmail.com> <20100505061620.GA2381@osiris.boeblingen.de.ibm.com> <4BE123B1.1050500@linux.vnet.ibm.com> In-Reply-To: <4BE123B1.1050500@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Stefan Weinhuber Cc: Heiko Carstens , Xose Vazquez Perez , Stefan Weinhuber , Horst Hummel , Stefan Haberland , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: 05.05.2010 11:52, Stefan Weinhuber wrote: >> On Mon, Apr 26, 2010 at 02:34:16PM +0200, Xose Vazquez Perez wrote: >>> hi, >>> >>> why is it FORCED ? bypassing a GLOBAL setting and also the kernel >>> command line !!! > > At the time this change was made we had the problem that the > default scheduler chosen by the distributions resulted in > bad performance for DASD devices. > I don't know what options were considered back then, but > I think that having the device driver set a driver specific default > is better than forcing the whole system to use 'our' scheduler. > > I agree that hard coding this choice into the driver is not pretty, > but it is pragmatic. Some generic mechanism for setting driver specific > defaults would be nicer, but I doubt that many other drivers would > actually benefit from such an interface. See also another thread started just two days ago: http://lkml.org/lkml/2010/5/3/404 Just... one more data point... ;) /mjt