Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759142AbYA3Qet (ORCPT ); Wed, 30 Jan 2008 11:34:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751544AbYA3Qej (ORCPT ); Wed, 30 Jan 2008 11:34:39 -0500 Received: from accolon.hansenpartnership.com ([76.243.235.52]:46005 "EHLO accolon.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751492AbYA3Qei (ORCPT ); Wed, 30 Jan 2008 11:34:38 -0500 Subject: Re: Integration of SCST in the mainstream Linux kernel From: James Bottomley To: Bart Van Assche Cc: FUJITA Tomonori , rdreier@cisco.com, torvalds@linux-foundation.org, akpm@linux-foundation.org, vst@vlnb.net, linux-scsi@vger.kernel.org, scst-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org In-Reply-To: References: <1201639331.3069.58.camel@localhost.localdomain> <20080130083239E.fujita.tomonori@lab.ntt.co.jp> Content-Type: text/plain Date: Wed, 30 Jan 2008 10:34:31 -0600 Message-Id: <1201710871.3292.22.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 (2.12.3-1.fc8) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1329 Lines: 32 On Wed, 2008-01-30 at 09:38 +0100, Bart Van Assche wrote: > On Jan 30, 2008 12:32 AM, FUJITA Tomonori wrote: > > > > iSER has parameters to limit the maximum size of RDMA (it needs to > > repeat RDMA with a poor configuration)? > > Please specify which parameters you are referring to. As you know I > had already repeated my tests with ridiculously high values for the > following iSER parameters: FirstBurstLength, MaxBurstLength and > MaxRecvDataSegmentLength (16 MB, which is more than the 1 MB block > size specified to dd). the 1Mb block size is a bit of a red herring. Unless you've specifically increased the max_sector_size and are using an sg_chain converted driver, on x86 the maximum possible transfer accumulation is 0.5MB. I certainly don't rule out that increasing the transfer size up from 0.5MB might be the way to improve STGT efficiency, since at an 1GB/s theoretical peak, that's roughly 2000 context switches per I/O; however, It doesn't look like you've done anything that will overcome the block layer limitations. James -- 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/