Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752659Ab0HYTNN (ORCPT ); Wed, 25 Aug 2010 15:13:13 -0400 Received: from moutng.kundenserver.de ([212.227.17.9]:50912 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751771Ab0HYTNK (ORCPT ); Wed, 25 Aug 2010 15:13:10 -0400 Message-ID: <4C756B37.4000007@vlnb.net> Date: Wed, 25 Aug 2010 23:12:55 +0400 From: Vladislav Bolkhovitin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.10) Gecko/20100527 Thunderbird/3.0.5 MIME-Version: 1.0 To: Chris Worley CC: =?ISO-8859-1?Q?Pasi_K=E4rkk=E4inen?= , Chetan Loke , Bart Van Assche , linux-scsi@vger.kernel.org, LKML , James Bottomley , scst-devel Subject: Re: Linux I/O subsystem performance References: <8A96806D-6CD7-44AD-8A9D-143C098C95A4@uni-paderborn.de> <1282256949.30453.278.camel@haakon2.linux-iscsi.org> <4C701E08.2020005@vlnb.net> <1282423398.3015.39.camel@mulgrave.site> <1282508953.3042.102.camel@mulgrave.site> <4C727BEB.9020100@scalableinformatics.com> <20100824072557.GK2804@reaktio.net> <4C7404C4.4040704@vlnb.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:GjNEcN/X2VYXSzWJ3ULJ1pYnqyrMW5JE7yiYP9EnzxN m4voMtjN5WbI1ggi8XsidB1l/VrCotv0MF7LyrWzrCJ3hvdytD JngFRCODs0NpUGqZl1o/s3B75jWpm49pYavcegSGTz2yq5EYf5 gOHzIvt2kd4g46FKYYuqX5ryBoRKP8adoh4MZzslCmCHBIYMYT EpH7EGXm8iT6oca9DmpIQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1586 Lines: 34 Chris Worley, on 08/25/2010 12:31 AM wrote: >> I also have an impression that Linux I/O subsystem has some performance >> problems. For instance, in one recent SCST performance test only 8 Linux >> initiators with fio as a load generator were able to saturate a single SCST >> target with dual IB cards (SRP) on 4K AIO direct accesses over an SSD >> backend. This rawly means that any initiator took several times (8?) more >> processing time than the target. > > While I can't tell you where the bottlenecks are, I can share some > performance numbers... > > 4 initiators can get>600K random 4KB IOPS off a single target... Hmm, on the data you sent me only 8 initiators were capable to do so... I'm glad to see an improvement here ;). > which is ~150% of what the Emulex/Intel/Microsoft results show using 8 > targets at 4KB (their 1M IOPS was at 512 byte blocks, which is not a > realistic test point From my, a storage developer's, POV it isn't about if this test is realistic or not. 512 bytes tests are good if you want to test how processing effective your I/O stack, because they produce the max possible CPU/memory/hardware interaction load. Since processing power isn't unlimited, in case if it is a bottleneck, N IOPS on 512b < N IOPS on 4K * 8 and system with more effective processing will have better numbers. Vlad -- 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/