From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bart Van Assche" Subject: Re: Integration of SCST in the mainstream Linux kernel Date: Tue, 5 Feb 2008 20:02:06 +0100 Message-ID: References: <47A89889.9060701@Voltaire.COM> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from el-out-1112.google.com ([209.85.162.182]:2145 "EHLO el-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755292AbYBETCI (ORCPT ); Tue, 5 Feb 2008 14:02:08 -0500 Received: by el-out-1112.google.com with SMTP id v27so886792ele.23 for ; Tue, 05 Feb 2008 11:02:07 -0800 (PST) In-Reply-To: <47A89889.9060701@Voltaire.COM> Content-Disposition: inline Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Erez Zilber Cc: Linus Torvalds , Andrew Morton , Vladislav Bolkhovitin , James.Bottomley@hansenpartnership.com, FUJITA Tomonori , linux-scsi@vger.kernel.org, scst-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org On Feb 5, 2008 6:10 PM, Erez Zilber wrote: > One may claim that STGT should have lower performance than SCST because > its data path is from userspace. However, your results show that for > non-IB transports, they both show the same numbers. Furthermore, with IB > there shouldn't be any additional difference between the 2 targets > because data transfer from userspace is as efficient as data transfer > from kernel space. > > The only explanation that I see is that fine tuning for iSCSI & iSER is > required. As was already mentioned in this thread, with SDR you can get > ~900 MB/sec with iSER (on STGT). My most recent measurements also show that one can get 900 MB/s with STGT + iSER on an SDR IB network, but only for very large block sizes (>= 100 MB). A quote from Linus Torvalds is relevant here (February 5, 2008): Block transfer sizes over about 64kB are totally irrelevant for 99% of all people. Please read my e-mail (posted earlier today) with a comparison for 4 KB - 64 KB block transfer sizes between SCST and STGT. Bart Van Assche.