Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763604AbZDAMUp (ORCPT ); Wed, 1 Apr 2009 08:20:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763036AbZDAMU2 (ORCPT ); Wed, 1 Apr 2009 08:20:28 -0400 Received: from wa-out-1112.google.com ([209.85.146.179]:10426 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762910AbZDAMU0 (ORCPT ); Wed, 1 Apr 2009 08:20:26 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=references:message-id:from:to:in-reply-to:content-type :content-transfer-encoding:x-mailer:mime-version:subject:date:cc; b=kCJQNWLCigQhVT4J90degfHEB6LUdRV3YWW0x3E3lSGAQtCbXer3IKHdBhOmG81i9H 6A7i+DlnO6p0NMIZg8BMmL0W9ZbQcmb9wQZkLrZOxwRPL0gprZVki4s9L/1YqJw9kYQc Btegbwua417jJMhAKLv6LfRmLGycnUguU/1pc= References: <49D10256.8030307@vlnb.net> <49D11096.3070804@vlnb.net> <49D254E4.8050806@vlnb.net> Message-Id: From: Ross Walker To: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit X-Mailer: iPhone Mail (5H11) Mime-Version: 1.0 (iPhone Mail 5H11) Subject: Re: [Iscsitarget-devel] [Scst-devel] ISCSI-SCST performance (withalso IET and STGT data) Date: Wed, 1 Apr 2009 08:20:14 -0400 Cc: "Ross S. W. Walker" , Vladislav Bolkhovitin , "linux-scsi@vger.kernel.org" , iSCSI Enterprise Target Developer List , "linux-kernel@vger.kernel.org" , "stgt@vger.kernel.org" , scst-devel Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1361 Lines: 34 On Apr 1, 2009, at 2:29 AM, Bart Van Assche wrote: > On Tue, Mar 31, 2009 at 8:43 PM, Ross S. W. Walker > wrote: >> IET just needs to fix how it does it workload with CFQ which >> somehow SCST has overcome. Of course SCST tweaks the Linux kernel to >> gain some extra speed. > > I'm not familiar with the implementation details of CFQ, but I know > that one of the changes between SCST 1.0.0 and SCST 1.0.1 is that the > default number of kernel threads of the scst_vdisk kernel module has > been increased to 5. Could this explain the performance difference > between SCST and IET for FILEIO and BLOCKIO ? Thank for the update. IET has used 8 threads per target for ages now, I don't think it is that. It may be how the I/O threads are forked in SCST that causes them to be in the same I/O context with each other. I'm pretty sure implementing a version of the patch that was used for the dump command (found on the LKML) will fix this. But thanks goes to Vlad for pointing this dificiency out so we can fix it to help make IET even better. -Ross -- 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/