Date: Sat, 12 Jul 2014 12:33:23 +0000 From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: =?windows-1252?Q?Olivier_Cochard-Labb=E9?= <olivier@cochard.me> Cc: FreeBSD Net <freebsd-net@freebsd.org>, John Jasem <jjasen@gmail.com>, Navdeep Parhar <nparhar@gmail.com> Subject: Re: tuning routing using cxgbe and T580-CR cards? Message-ID: <68918930-4FEC-413B-AB5E-B544C936D54F@lists.zabbadoz.net> In-Reply-To: <CA%2Bq%2BTcpv_UqWCT1z9yimqUYw_TqmQad=8Mirh8VWexMdQ4JGWA@mail.gmail.com> References: <53C01EB5.6090701@gmail.com> <01AABF44-4801-45B5-9509-1CA7BAA3CB30@lists.zabbadoz.net> <CA%2Bq%2BTcpv_UqWCT1z9yimqUYw_TqmQad=8Mirh8VWexMdQ4JGWA@mail.gmail.com>
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On 12 Jul 2014, at 12:17 , Olivier Cochard-Labb=E9 <olivier@cochard.me> = wrote: > On Fri, Jul 11, 2014 at 8:03 PM, Bjoern A. Zeeb < > bzeeb-lists@lists.zabbadoz.net> wrote: >=20 >> If you are primarily forwarding packets (you say "routing" multiple = times) >> the first thing you should do is turn off LRO and TSO on all ports. >>=20 >=20 > Hi Bjoern, >=20 > I was not aware of disabling LRO+TSO for forwarding packet. > If I read correctly the wikipedia page of LRO[1]: Disabling LRO is not = a > concern of performance but only of not breaking the end-to-end = principle, > right ? > But regarding TSO[2]: It should improve performance only between the = TCP > and IP layer. But paquet forwarded didn't have to cross TCP<->IP = layer, > then disabling TSO should not impact performance, right ? For forwarding it means that you are re-assembling a packet on receive, = buffering multiple, etc, then hand them up the stack, only to find that = you are sending it out again, and thus you break them into multiple = packets again. In other words: you do a lot more work and add latency = than you need/want. I seem to remember that we added the knob to automatically disable our = soft-LRO when forwarding is turned on (but I haven=92t checked if I = really did). If we did, at least for soft-LRO you won=92t notice a = difference indeed. > - Multi-flows (different UDP ports) of small packet (60B) at about = 10Mpps > =85 > No difference proven at 95.0% confidence >=20 > =3D> There is not difference: Then I can disable LRO for respecting = the > end-to-end principle. But why disabling TSO ? Try TCP flows. =97=20 Bjoern A. Zeeb "Come on. Learn, goddamn it.", WarGames, 1983
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