ovs-netmap forgotten?

Vincenzo Maffione v.maffione at gmail.com
Wed Jun 7 21:04:17 UTC 2017


You can play with NIC interrupt coalescing settings to keep them under
control (I don't know how in FreeBSD, but in Linux you would do that with
e.g. "ethtool -C rx-usecs 100").
As written in the last line of netmap(4), you must disable all the
offloadings when playing with netmap physical ports.

By the way, there is a person working on adding some offloading support to
netmap, but this is still in progress and it is not even in the netmap
github yet.

Cheers,
  Vincenzo

2017-06-06 11:59 GMT+02:00 Harry Schmalzbauer <freebsd at omnilan.de>:

>  Bezüglich Harry Schmalzbauer's Nachricht vom 05.06.2017 20:25 (localtime):
> > Bezüglich Vincenzo Maffione's Nachricht vom 05.06.2017 16:06 (localtime):
> >
>> > First quick test shows you're right and this tiny diff solves a decent
> > share of my (ESXi-replacing) problems:
> >
> > --- src/sys/net/if_vlan.c.orig  2017-06-05 17:39:27.770574000 +0200
> > +++ src/sys/net/if_vlan.c       2017-06-05 17:39:21.550278000 +0200
> > @@ -1234,7 +1234,7 @@
> >         if_inc_counter(ifv->ifv_ifp, IFCOUNTER_IPACKETS, 1);
> >
> >         /* Pass it back through the parent's input routine. */
> > -       (*ifp->if_input)(ifv->ifv_ifp, m);
> > +       (*ifv->ifv_ifp->if_input)(ifv->ifv_ifp, m);
> >  }
> >
> >  static int
> >
> > Will do real-world tests tommorrow.
>
> To share my observations:
>
> Attaching if_vlan(4) to vale(4) works with the above modification, as
> long as vlanhwtag is _not_ disabled, at least with igb(4) and (em4).
> Having other offloadings enabled or disabled (regardless if it's on
> parent or vlan-clone) doesn't matter, disabling vlanhwtag on the parent
> leads to congested parent if there's mor etraffic than console... I
> haven't done any tracking if it's caused by TCP windows scaling e.g. nor
> tried to ask the code, because I do want vlanhwtagging enabled and
> that's what works so far :-)
> This is also true for if_vlan(4) interfaces which have if_lagg(0) as
> parent, and also for both types of vale(4) attaching, hoststack-detached
> (-a) or hoststack-attached (-h).
> So far very nice :-)
>
> But there's a interrupt multiplication noticeable (at the host).
>
> My simple NFS-copying test causes ~10ki/s at one igb(4) queue when
> invoked on the host, with mtu 1500.
> Same invocation in the guest, with vlan-vale setup, causes 30ki/s
> average (with high discrepancy, 20-40k).
>
> Might it be possible that if_vlan(4) influences interrupt moderation
> capabilities?
>
> Vincenzo, thanks for your answers to my questions, which I read during
> writing of this - stripping them here.
>
> -harry
>



-- 
Vincenzo Maffione


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