From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: [PATCH v2 net-next] net: introduce gro_frag_list_enable sysctl Date: Wed, 30 Oct 2013 14:09:54 -0400 Message-ID: <52714B72.2060200@redhat.com> References: <1383059555.5464.33.camel@edumazet-glaptop.roam.corp.google.com> <20131029.194446.2215574000648693370.davem@davemloft.net> <1383094428.4857.16.camel@edumazet-glaptop.roam.corp.google.com> <20131029.220253.1263087684709722001.davem@davemloft.net> <1383106012.4857.26.camel@edumazet-glaptop.roam.corp.google.com> <20131030040818.GB2755@gondor.apana.org.au> <1383106577.4857.30.camel@edumazet-glaptop.roam.corp.google.com> <20131030041959.GA3162@gondor.apana.org.au> <1383107681.4857.33.camel@edumazet-glaptop.roam.corp.google.com> <20131030044212.GA3364@gondor.apana.org.au> Reply-To: vyasevic@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , David Miller , Christoph Paasch , "netdev@vger.kernel.org" , Michael Dalton To: Jerry Chu , Herbert Xu Return-path: Received: from mx1.redhat.com ([209.132.183.28]:37234 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751685Ab3J3SKU (ORCPT ); Wed, 30 Oct 2013 14:10:20 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 10/30/2013 01:39 PM, Jerry Chu wrote: > On Tue, Oct 29, 2013 at 9:42 PM, Herbert Xu wrote: >> >> On Tue, Oct 29, 2013 at 09:34:41PM -0700, Eric Dumazet wrote: >>> >>> What matters ? >>> >>> GRO ? >> >> What matters is that you should not treat the forwarding case >> separately from the host case. >> >> For virtualisation the host case looks exactly like the forwarding >> case. > > > Not sure I agree - there are two different "forwarding" cases - forwarding > to another physical NIC (to go out to the wire hence need to do GSO), > and (for virtualization) forwarding to a virtual NIC and consumed internally > (e.g., VM). I don't think you can really differentiate these 2 case. VM are very commonly used as routers/forwarders. In some cases, to get better throughput, VFs are assigned to the VMs as the externally facing ports. So, you still end up forwarding to another physical NIC. -vlad > For the latter we should strive to push GSO pkts all the way > to the VM stack w/o breaking them up. So for virtualization GRO is all > goodness but not sure about the regular forwarding path. (From the > perf perspective it boils down to if the cost of GSO/GRO will offset > the benefit of GRO. Sure if one manages to get the cost close to zero > than there is not reason to leave GRO always on. But it's still a big if for > now.) > > Best, > > Jerry > >> >> >> IOW, if having a 64KB packet matters for the host, then it matters >> for forwarding as well. >> >>> Before my patch, GRO packets were 17 MSS, and nobody complained packets >>> were too small, so what are you saying exactly ? >> >> I'm not criticsing your mega-GRO patch at all. That one is great >> and means that we'll get aggregated packets up to 64K. What we need >> to do is just to patch up the GSO code so that it can handle these >> mega-packets properly. >> >> Cheers, >> -- >> Email: Herbert Xu >> Home Page: http://gondor.apana.org.au/~herbert/ >> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >