Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759830AbZDBOH0 (ORCPT ); Thu, 2 Apr 2009 10:07:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754924AbZDBOHK (ORCPT ); Thu, 2 Apr 2009 10:07:10 -0400 Received: from mailgw.nyc.medallion.com ([63.68.220.242]:2614 "EHLO mailgw.nyc.medallion.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754573AbZDBOHI convert rfc822-to-8bit (ORCPT ); Thu, 2 Apr 2009 10:07:08 -0400 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.4325 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Subject: RE: [Scst-devel] [Iscsitarget-devel] ISCSI-SCST performance (with also IET and STGT data) Date: Thu, 2 Apr 2009 10:06:59 -0400 Message-ID: In-Reply-To: <49D47F28.3060409@vlnb.net> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [Scst-devel] [Iscsitarget-devel] ISCSI-SCST performance (with also IET and STGT data) Thread-Index: AcmzccVXprZxray5RuGN9SHeXbCCpAAKSY+w References: <49D10256.8030307@vlnb.net> <49D11096.3070804@vlnb.net> <49D254E4.8050806@vlnb.net>

<1238617423.3318.82.camel@mulgrave.int.hansenpartnership.com> <49D46B8B.5000708@vlnb.net> <49D47F28.3060409@vlnb.net> From: "Ross S. W. Walker" Importance: normal To: "Vladislav Bolkhovitin" , "James Bottomley" Cc: , "iSCSI Enterprise Target Developer List" , , "Ross Walker" , "scst-devel" , X-OriginalArrivalTime: 02 Apr 2009 14:06:59.0701 (UTC) FILETIME=[4A257A50:01C9B39C] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2988 Lines: 75 Vladislav Bolkhovitin wrote: > Vladislav Bolkhovitin, on 04/02/2009 11:38 AM wrote: > > James Bottomley, on 04/02/2009 12:23 AM wrote: > >> > >> SCST explicitly fiddles with the io context to get this to happen. It > >> has a hack to block to export alloc_io_context: > >> > >> http://marc.info/?t=122893564800003 > > > > Correct, although I wouldn't call it "fiddle", rather "grouping" ;) Call it what you like, Vladislav Bolkhovitin wrote: > Ross S. W. Walker, on 03/30/2009 10:33 PM wrote: > > I would be interested in knowing how your code defeats CFQ's extremely > high latency? Does your code reach into the io scheduler too? If not, > some code hints would be great. Hmm, CFQ doesn't have any extra processing latency, especially "extremely", hence there is nothing to defeat. If it had, how could it been chosen as the default? ---------- List: linux-scsi Subject: [PATCH][RFC 13/23]: Export of alloc_io_context() function From: Vladislav Bolkhovitin Date: 2008-12-10 18:49:19 Message-ID: 49400F2F.4050603 () vlnb ! net This patch exports alloc_io_context() function. For performance reasons SCST queues commands using a pool of IO threads. It is considerably better for performance (>30% increase on sequential reads) if threads in a pool have the same IO context. Since SCST can be built as a module, it needs alloc_io_context() function exported. ---------- I call that lying. > > But that's not the only reason for good performance. Particularly, it > > can't explain Bart's tmpfs results from the previous message, where the > > majority of I/O done to/from RAM without any I/O scheduler involved. (Or > > does I/O scheduler also involved with tmpfs?) Bart has 4GB RAM, if I > > remember correctly, i.e. the test data set was 25% of RAM. > > To remove any suspicions that I'm playing dirty games here I should note I don't know what games your playing at, but do me a favor, if your too stupid enough to realize when your caught in a lie and to just shut up then please do me the favor and leave me out of any further correspondence from you. Thank you, -Ross ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof. -- 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/