From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH v2] ipv4: Early TCP socket demux. Date: Wed, 20 Jun 2012 23:17:56 +0200 Message-ID: <1340227076.4604.1905.camel@edumazet-glaptop> References: <1340171940.4604.799.camel@edumazet-glaptop> <1340215664.2576.12.camel@bwh-desktop.uk.solarflarecom.com> <1340217604.4604.1569.camel@edumazet-glaptop> <20120620.140121.1603737472432326278.davem@davemloft.net> <20120620140454.36847c65@s6510.linuxnetplumber.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Miller , bhutchings@solarflare.com, netdev@vger.kernel.org To: Stephen Hemminger Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:56261 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755093Ab2FTVSC (ORCPT ); Wed, 20 Jun 2012 17:18:02 -0400 Received: by bkcji2 with SMTP id ji2so6692769bkc.19 for ; Wed, 20 Jun 2012 14:18:00 -0700 (PDT) In-Reply-To: <20120620140454.36847c65@s6510.linuxnetplumber.net> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2012-06-20 at 14:04 -0700, Stephen Hemminger wrote: > On Wed, 20 Jun 2012 14:01:21 -0700 (PDT) > David Miller wrote: > > > From: Eric Dumazet > > Date: Wed, 20 Jun 2012 20:40:04 +0200 > > > > > If someone wants to tune its linux router, he probably already disables > > > GRO because of various issues with too big packets. > > > > > > GRO adds a significant cost to forwarding path. > > > > No, Ben is right Eric. GRO decreases the costs, because it means we > > only need to make one forwarding/netfilter/classification decision for > > N packets instead of 1. > > GRO is also important for routers that interact with VM's. > It helps reduce the per-packet wakeup of the guest VM's. I spoke of mere routers, I was _not_ saying GRO is useless. In most routers setups I used, I had to disable GRO, because 64Kbytes packets on output path broke the tc setups (SFQ) netfilter cost was hardly a problem, once correctly done.