From owner-freebsd-current@FreeBSD.ORG Thu Oct 2 22:40:04 2008 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2A4871065687; Thu, 2 Oct 2008 22:40:04 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.freebsd.org (Postfix) with ESMTP id 2A5618FC27; Thu, 2 Oct 2008 22:40:02 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from phobos.local ([192.168.254.200]) (authenticated bits=0) by pooker.samsco.org (8.14.2/8.14.2) with ESMTP id m92MdumS091638; Thu, 2 Oct 2008 16:39:56 -0600 (MDT) (envelope-from scottl@samsco.org) Message-ID: <48E54DBC.5030005@samsco.org> Date: Thu, 02 Oct 2008 16:39:56 -0600 From: Scott Long User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.8.1.13) Gecko/20080313 SeaMonkey/1.1.9 MIME-Version: 1.0 To: John Baldwin References: <2DC640DB-2B7C-4111-9842-BDFA3E134282@panasas.com> <200810021553.12976.jhb@freebsd.org> In-Reply-To: <200810021553.12976.jhb@freebsd.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.4 required=3.8 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.1.8 X-Spam-Checker-Version: SpamAssassin 3.1.8 (2007-02-13) on pooker.samsco.org Cc: Joel Jacobson , freebsd-current@freebsd.org Subject: Re: scatter/gather in struct buf/bio X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Oct 2008 22:40:04 -0000 John Baldwin wrote: > On Thursday 02 October 2008 02:11:38 pm Joel Jacobson wrote: >> Greetings - >> >> I have something which would be vastly improved by the ability to >> construct my own sgl to pass through a buf, and ran across: >> >> http://wiki.freebsd.org/Buf0x >> >> Is there somewhere I can follow progress, and/or contribute assistance? > > The jhb_bio branch still exists. I've made some refinements to the sglist API > and need to do so more. I think my next test will be to add a sglist to each > bio in geom_disk and geom_vfs. I then might try to update physio (dd > if=/dev/XXX) to not map buffers into KVA (probably tweakable via sysctl) and > patch ATA to use the new bus dma call with the sglist in the bio and see what > difference that makes. > Doing a single dd probably isn't going to show any difference at all. That won't mean that the changes aren't worthwhile, it'll just mean that you're testing the seek latency of the disk, which is a property that is reliably static. Please talk to me in private about effective ways to do performance testing for something like this. Scott