Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752372AbZKPKrn (ORCPT ); Mon, 16 Nov 2009 05:47:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752296AbZKPKrm (ORCPT ); Mon, 16 Nov 2009 05:47:42 -0500 Received: from cantor2.suse.de ([195.135.220.15]:52485 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751987AbZKPKrm (ORCPT ); Mon, 16 Nov 2009 05:47:42 -0500 Date: Mon, 16 Nov 2009 11:47:44 +0100 From: Jan Kara To: Jeff Moyer Cc: Jan Kara , jens.axboe@oracle.com, LKML , Chris Mason , Andrew Morton , Mike Galbraith , mszeredi@suse.de Subject: Re: Performance regression in IO scheduler still there Message-ID: <20091116104744.GC23231@duck.suse.cz> References: <20091026172012.GC7233@duck.suse.cz> <20091111141031.GA21511@duck.suse.cz> <20091112172941.GK14528@duck.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1933 Lines: 46 On Thu 12-11-09 15:44:02, Jeff Moyer wrote: > Jan Kara writes: > > > On Wed 11-11-09 12:43:30, Jeff Moyer wrote: > >> Jan Kara writes: > >> > >> > Sadly, I don't see the improvement you can see :(. The numbers are the > >> > same regardless low_latency set to 0: > >> > 2.6.32-rc5 low_latency = 0: > >> > 37.39 36.43 36.51 -> 36.776667 0.434920 > >> > But my testing environment is a plain SATA drive so that probably > >> > explains the difference... > >> > >> I just retested (10 runs for each kernel) on a SATA disk with no NCQ > >> support and I could not see a difference. I'll try to dig up a disk > >> that support NCQ. Is that what you're using for testing? > > I don't think I am. How do I find out? > > Good question. ;-) I grep for NCQ in dmesg output and make sure it's > greater than 0/32. There may be a better way, though. Message in the logs: ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300) ata1.00: ATA-8: Hitachi HTS722016K9SA00, DCDOC54P, max UDMA/133 ata1.00: 312581808 sectors, multi 16: LBA48 NCQ (depth 0/32) ata1.00: configured for UDMA/133 So apparently no NCQ. /sys/block/sda/device/queue_depth shows 1 but I guess that's just it's way of saying "no NCQ". What I thought might make a difference why I'm seeing the drop and you are not is size of RAM or number of CPUs vs the tiobench file size or number of threads. I'm running on a machine with 2 GB of RAM, using 4 GB filesize. The machine has 2 cores and I'm using 16 tiobench threads. I'm now rerunning tests with various numbers of threads to see how big difference it makes. Honza Honza -- Jan Kara SUSE Labs, CR -- 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/