From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Re: Why is LRO off by default on ixgbe? Date: Wed, 23 Sep 2009 10:16:01 -0700 Message-ID: <4ABA57D1.5000905@candelatech.com> References: <4ABA4D07.50107@candelatech.com> <20090923095356.7f9aef37@s6510> <4ABA538F.7020507@candelatech.com> <20090923100718.79877040@s6510> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: NetDev To: Stephen Hemminger Return-path: Received: from mail.candelatech.com ([208.74.158.172]:37816 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752175AbZIWRP6 (ORCPT ); Wed, 23 Sep 2009 13:15:58 -0400 In-Reply-To: <20090923100718.79877040@s6510> Sender: netdev-owner@vger.kernel.org List-ID: On 09/23/2009 10:07 AM, Stephen Hemminger wrote: > On Wed, 23 Sep 2009 09:57:51 -0700 > Ben Greear wrote: > >> On 09/23/2009 09:53 AM, Stephen Hemminger wrote: >>> On Wed, 23 Sep 2009 09:29:59 -0700 >>> Ben Greear wrote: >>> >>>> I just noticed that enabling LRO on ixgbe lets me reach about 9Gbps receive on two >>>> NICs concurrently in an NFS test, where I was only getting about 6Gbps w/out it (1500 MTU). >>>> >>>> Why is LRO disabled by default? >>>> >>>> Thanks, >>>> Ben >>> >>> LRO is turned off if bridging or routing because of End to End requirements. >> >> That makes sense. >> >> If I know that all interfaces in question can handle TSO and LRO, >> I could manually enable LRO w/out risk, right? >> > > The problem is that LRO merges TCP packets, this breaks the end-to-end > ack clocking and checksumming, and therefore is not enabled. > That is why GRO is the replacement solution (preserves packet boundaries) Ok. It seems GRO was enabled the whole time, but LRO is what gave me the extra performance boost. In this particular case, I'm not actually routing, though I do have ip-forward enabled, so I guess LRO will be OK as long as I'm careful... Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com