From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Andr=E9_Tomt?= Subject: Re: [git patches] IDE update Date: Tue, 05 Jul 2005 01:25:33 +0200 Message-ID: <42C9C56D.7040701@tomt.net> References: <200507042033.XAA19724@raad.intranet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail1.skjellin.no ([80.239.42.67]:43936 "EHLO mx1.skjellin.no") by vger.kernel.org with ESMTP id S261731AbVGDXZh (ORCPT ); Mon, 4 Jul 2005 19:25:37 -0400 In-Reply-To: <200507042033.XAA19724@raad.intranet> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Al Boldi Cc: 'Bartlomiej Zolnierkiewicz' , 'Ondrej Zary' , 'Linus Torvalds' , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Al Boldi wrote: > Bartlomiej Zolnierkiewicz wrote: { > >>>>On 7/4/05, Al Boldi wrote: >>>>Hdparm -tT gives 38mb/s in 2.4.31 >>>>Cat /dev/hda > /dev/null gives 2% user 33% sys 65% idle >>>> >>>>Hdparm -tT gives 28mb/s in 2.6.12 >>>>Cat /dev/hda > /dev/null gives 2% user 25% sys 0% idle 73% IOWAIT The "hdparm doesn't get as high scores as in 2.4" is a old discussed to death "problem" on LKML. So far nobody has been able to show it affects anything but that pretty useless quasi-benchmark. >>>>It feels like DMA is not being applied properly in 2.6.12. >>> >>>Same on 2.6.10,11,12. >>>No errors though, only sluggish system. Really sluggish or just "benchmark-sluggish"? If the former, try selecting a different IO elevator/sheduler. If the latter it doesn't matter much, at least not with the very simple hdparm test :-) >> >> What about earlier kernels? >> Please try to narrow down the problem to a specific kernel version. >> } > > Don't know about 2.6.0-2.6.9, but 2.4.31 is ok. > > Bartlomiej, > When you compare 2.4.31 with 2.6.12 don't you see this problem on your > machine? > If you have a fast system the slowdown won't show, but your IOWAIT will be > higher anyway! Nothing wrong with 73% iowait, I'd even consider it very low while putting load on a harddrive. Its just time spent waiting for data to be returned from disk, and thus I usually expect no lower than ~98-99% while stressing any disk. Harddisks are _slow as snails_ compared to cpu cycles ;-) Beware 2.4 didn't export that statistic at all to userspace, so 0% iowait gets reported from most 2.6-ready reporting tools on 2.4.