Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263563AbUDPQ5a (ORCPT ); Fri, 16 Apr 2004 12:57:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263557AbUDPQ51 (ORCPT ); Fri, 16 Apr 2004 12:57:27 -0400 Received: from smtp.rol.ru ([194.67.21.9]:49467 "EHLO smtp.rol.ru") by vger.kernel.org with ESMTP id S263425AbUDPQ5I (ORCPT ); Fri, 16 Apr 2004 12:57:08 -0400 From: Konstantin Sobolev Reply-To: kos@supportwizard.com Organization: SupportWizard To: Denis Vlasenko Subject: Re: poor sata performance on 2.6 Date: Fri, 16 Apr 2004 20:59:44 +0400 User-Agent: KMail/1.6.1 Cc: Jeff Garzik , Justin Cormack , Ryan Geoffrey Bourgeois , Kernel mailing list , linux-ide@vger.kernel.org References: <200404150236.05894.kos@supportwizard.com> <407F315E.2000809@pobox.com> <200404161748.38958.vda@port.imtp.ilyichevsk.odessa.ua> In-Reply-To: <200404161748.38958.vda@port.imtp.ilyichevsk.odessa.ua> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="koi8-r" Content-Transfer-Encoding: 8BIT Message-Id: <200404162059.44465.kos@supportwizard.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2723 Lines: 70 On Friday 16 April 2004 18:48, Denis Vlasenko wrote: > > When you mount a filesystem, it changes the default block size (512 or > > 1024) to the filesystem block size, normally 4096. This would certainly > > increase the throughput. > > Yes, this works. > > But if one uses unpartitioned disk, why does (s)he need to > do some blocksize tricks before hdparm starts to measure good performance? > I think that in this case block layer can coalesce small read requests > into large ones regardless of block size. > > Konstantin, does dd give you the same behaviour as hdparm? Sorry, I already partitioned it and put lots of data there. But situation is reproducible by removing all /dev/sda entries from fstab and rebooting. Here are results of my experiments with dd: kos root # bash -c "sleep 10 && killall -3 dd &" && LANG=C time dd if=/dev/sda of=/dev/null ibs=512 obs=512 537152+0 records in 537152+0 records out Command terminated by signal 3 0.23user 3.73system 0:10.07elapsed 39%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+121minor)pagefaults 0swaps kos root # hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 84 MB in 3.07 seconds = 27.37 MB/sec kos root # bash -c "sleep 10 && killall -3 dd &" && LANG=C time dd if=/dev/sda of=/dev/null ibs=4096 obs=4096 71691+0 records in 71691+0 records out Command terminated by signal 3 0.07user 3.83system 0:10.08elapsed 38%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+122minor)pagefaults 0swaps kos root # mount /dev/sda2 /wd kos root # hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 84 MB in 3.07 seconds = 27.38 MB/sec kos root # hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 206 MB in 3.02 seconds = 68.13 MB/sec kos root # bash -c "sleep 10 && killall -3 dd &" && LANG=C time dd if=/dev/sda of=/dev/null ibs=512 obs=512 1402384+0 records in 1402384+0 records out Command terminated by signal 3 0.54user 2.57system 0:10.02elapsed 31%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+121minor)pagefaults 0swaps kos root # bash -c "sleep 10 && killall -3 dd &" && LANG=C time dd if=/dev/sda of=/dev/null ibs=4096 obs=4096 329705+0 records in 329705+0 records out Command terminated by signal 3 0.32user 2.43system 0:10.13elapsed 27%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+122minor)pagefaults 0swaps It looks like dd behaves similarly to hdparm -- /KoS * yas eh d'tahW. ??mih raeh uoy diD - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/