Dropping lro on the interfaces decreased interrupt usage on the CPUs, as measured by top -CHIPSu, by 15-20%, at least from eyeballing it. It did not otherwise have an effect on packet rates.
Thanks! On 07/12/2014 08:33 AM, Bjoern A. Zeeb wrote: > On 12 Jul 2014, at 12:17 , Olivier Cochard-Labbé <oliv...@cochard.me> wrote: > >> On Fri, Jul 11, 2014 at 8:03 PM, Bjoern A. Zeeb < >> bzeeb-li...@lists.zabbadoz.net> wrote: >> >>> 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. >>> >> Hi Bjoern, >> >> 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’t checked if I really > did). If we did, at least for soft-LRO you won’t notice a difference indeed. > > >> - Multi-flows (different UDP ports) of small packet (60B) at about 10Mpps >> … >> No difference proven at 95.0% confidence >> >> => There is not difference: Then I can disable LRO for respecting the >> end-to-end principle. But why disabling TSO ? > Try TCP flows. > > — > Bjoern A. Zeeb "Come on. Learn, goddamn it.", WarGames, 1983 > _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
