From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Zhang Subject: Re: Linux support for RDMA (was: [Ksummit-2005-discuss] Summary of 2005 Kernel Summit Proposed Topics) Date: Mon, 04 Apr 2005 08:58:20 -0400 Message-ID: <1112619500.2880.7.camel@localhost.localdomain> References: <67D69596DDF0C2448DB0F0547D0F947E01781F2E@yogi.asicdesigners.com> <1112576171.4227.5.camel@mylaptop> <20050404063456.GB30855@colo.lackof.org> <20050404001000.5fa8f206.davem@davemloft.net> Reply-To: mingz@ele.uri.edu Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Grant Grundler , Dmitry Yusupov , 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: <20050404001000.5fa8f206.davem@davemloft.net> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Mon, 2005-04-04 at 03:10, David S. Miller wrote: > On Mon, 4 Apr 2005 00:34:56 -0600 > Grant Grundler wrote: > > > Yes and No. PCI-X isn't fast enough but the data only crosses > > the PCI-X bus once. Think about the data flow: > > 1) DMA to RAM > > 2) load into CPU cache > > 3) store back into RAM > > > > We are down to 40% left...graphics folks won't like you. > > But you're missing the point, which is that the memory system > always catches up to the networking technology. > > We'll have that %60 back before you know it when we have > PCI-Z and DDR8 or whatever even in $500.00USD desktop machines. 10G is supposed to be deployed in 2005 and 2006. while i did not see DDR4 come out yet. > > And those systems will be present by the time we put together > this complicated infrastructure for RDMA. > > RDMA is like cache coloring page allocators, it's for yesterday's > technology that we won't be using tomorrow. :-) > > Those steps #2 and #3 in your data flow are powerful, it is what > gives us flexibility. And in a general purpose OS that is important.