From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Zhang Subject: RE: [Ksummit-2005-discuss] Summary of 2005 Kernel Summit ProposedTopics Date: Sat, 02 Apr 2005 14:14:47 -0500 Message-ID: <1112469286.4599.7.camel@localhost.localdomain> References: <67D69596DDF0C2448DB0F0547D0F947E01781F2E@yogi.asicdesigners.com> Reply-To: mingz@ele.uri.edu Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Dmitry Yusupov , "David S. Miller" , mpm@selenic.com, andrea@suse.de, michaelc@cs.wisc.edu, James.Bottomley@HansenPartnership.com, ksummit-2005-discuss@thunk.org, netdev@oss.sgi.com Return-path: To: open-iscsi In-Reply-To: <67D69596DDF0C2448DB0F0547D0F947E01781F2E@yogi.asicdesigners.com> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org yes, thx for explaining this in more detail. copy avoidance is one main goal of rdma. the BW gap is the bottleneck. ming On Sat, 2005-04-02 at 14:07, Asgeir Eiriksson wrote: > Dmitry > > The CPU cycles is only at most half of the story with the other half > being the memory sub-system BW. > > So the validity of your observation depends on the BW we're talking > about, i.e. if the client is using a fraction of 10Gbps for RDMA (or > DDP, e.g. iSCSI DDP), yes then that fraction amounts to a fraction of > the memory sub-system total BW so we don't much care about the extra > copy. > > The situation is different if the client wants something close to 10Gbps > (already have such client applications), because today 10Gbps is still a > big chunk of the overall memory BW so you really care about eliminating > that copy via DDP. > > 'Asgeir > > > -----Original Message----- > > From: netdev-bounce@oss.sgi.com [mailto:netdev-bounce@oss.sgi.com] On > > Behalf Of Dmitry Yusupov > > Sent: Saturday, April 02, 2005 10:09 AM > > To: open-iscsi@googlegroups.com > > Cc: David S. Miller; mpm@selenic.com; andrea@suse.de; > > michaelc@cs.wisc.edu; James.Bottomley@HansenPartnership.com; > ksummit-2005- > > discuss@thunk.org; netdev@oss.sgi.com > > Subject: Re: [Ksummit-2005-discuss] Summary of 2005 Kernel Summit > > ProposedTopics > > > > On Mon, 2005-03-28 at 17:32 -0500, Benjamin LaHaise wrote: > > > On Mon, Mar 28, 2005 at 12:48:56PM -0800, Dmitry Yusupov wrote: > > > > If you have plans to start new project such as SoftRDMA than yes. > lets > > > > discuss it since set of problems will be similar to what we've got > > with > > > > software iSCSI Initiators. > > > > > > I'm somewhat interested in seeing a SoftRDMA project get off the > ground. > > > At least the NatSemi 83820 gige MAC is able to provide early-rx > > interrupts > > > that allow one to get an rx interrupt before the full payload has > > arrived > > > making it possible to write out a new rx descriptor to place the > payload > > > wherever it is ultimately desired. It would be fun to work on if > not > > the > > > most performant RDMA implementation. > > > > I see a lot of skepticism around early-rx interrupt schema. It might > > work for gige, but i'm not sure if it will fit into 10g. > > > > What RDMA gives us is zero-copy on receive and new networking api > which > > has a potential to be HW accelerated. SoftRDMA will never avoid > copying > > on receive. But benefit for SoftRDMA would be its availability on > client > > sides. It is free and it could be easily deployed. Soon Intel & Co > will > > give us 2,4,8... multi-core CPUs for around 200$ :), So, who cares if > > one of those cores will do receive side copying? > > > >