From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Graf Subject: Re: [PATCH net-next 2/2] openvswitch: Use zerocopy if applicable when performing the upcall Date: Sat, 25 May 2013 08:02:22 +0100 Message-ID: <20130525070222.GB30252@casper.infradead.org> References: <064a09fffe48540b66a3ee503860ed9e8a1eb5f1.1369406826.git.tgraf@suug.ch> <1369421900.3301.431.camel@edumazet-glaptop> <1369432621.3301.445.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Dumazet , netdev , "dev@openvswitch.org" To: Jesse Gross Return-path: Received: from casper.infradead.org ([85.118.1.10]:38738 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750954Ab3EYHCY (ORCPT ); Sat, 25 May 2013 03:02:24 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 05/24/13 at 03:18pm, Jesse Gross wrote: > On Fri, May 24, 2013 at 2:57 PM, Eric Dumazet wrote: > >> My guess is that there isn't a real different for small packets since > >> everything will be in the cache but it seems worth checking given that > >> this is optimizing a rare case at the expense of the common one. > > > > I really doubt checksumming a SYN/ACK packet is that a performance > > issue. Do you have performance numbers ? > > > > You could always provide a patch to restore this copy/checksum if it > > really gives a benefit, and if people still use NIC not doing this > > checksum. > > If it makes a difference then it needs to be addressed before this > patch goes in since it's the common case. I don't think it will but > that's why I'm asking for numbers. I ran TCP_CRR to verify the SYN/ACK use case and I did not observe a difference. If you have any specific test in mind I will be glad to run that before posting the 2nd revision. The CPU numbers as reported was seen when testing with pktgen at 1400 bytes with 8K flows and a 10/8 random IP source address.