From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: Intel and TOE in the news Date: 22 Feb 2005 23:42:37 +0100 Message-ID: <20050222224237.GB60153@muc.de> References: <20050222214345.GA51890@muc.de> <200502222218.j1MMIVDD007619@guinness.s2io.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "'Stephen Hemminger'" , hadi@cyberus.ca, "'rick jones'" , netdev@oss.sgi.com, "'Alex Aizman'" Date: Tue, 22 Feb 2005 23:42:37 +0100 To: Leonid Grossman Content-Disposition: inline In-Reply-To: <200502222218.j1MMIVDD007619@guinness.s2io.com> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Tue, Feb 22, 2005 at 02:17:35PM -0800, Leonid Grossman wrote: > > > > -----Original Message----- > > From: Andi Kleen [mailto:ak@muc.de] > > Sent: Tuesday, February 22, 2005 1:44 PM > > To: Leonid Grossman > > Cc: 'Stephen Hemminger'; hadi@cyberus.ca; 'rick jones'; > > netdev@oss.sgi.com; 'Alex Aizman' > > Subject: Re: Intel and TOE in the news > > > > > TSO case is probably different - TSO hardware just sets PSH on the > > > last fragment only (and only if the flag was set on the > > original large > > > tx packet). Receiver doesn't really know if the sender is > > TSO-capable > > > or not and will ACK the same way - will it not? > > > Anyway, with LRO we do change rx packet count so affecting parts of > > > TCP that depend on packet count is indeed a concern; I guess we'll > > > find out soon enough whether there are real issues with the > > approach > > > :-) > > > > Linux doesn't depend on packet count; it keeps an estimate > > called rcv_mss about the biggest seen packet size and acks > > every 2*rcv_mss worth of data. > > > > Your scheme would likely result in acking every two of your > > large packets as soon as the connection is out of "quickack" > > mode. So there would be on wire differences. > > Sounds good, thanks! We should be OK then. Are you sure? It definitely wouldn't look like a conventional TCP ack clock on the wire, but you would get an ack only every (BIGPACKETSIZE/MSS) * 2 packets. Quite a stretch ACK. I'm not saying it wouldn't work (and maybe Rick et.al. are right and Acking overhead is the next TCP frontier), but it would be definitely quite different. It needs careful testing on how it behaves with packet loss. -Andi