dev.netmap.buf_size and packett size from host

[Luigi Rizzo]

Make sure you disable TSO on the interface used in netmap
mode, and then check that you use an MTU of 1500 on that
interface.
You should not receive frames larger than MTU coming from
the host in these conditions.

cheers
luigi


On Thu, Feb 4, 2016 at 3:26 PM, Eduardo Meyer <dudu.meyer at gmail.com> wrote:
> hello,
>
> I have a netmap application which has host mode bridge/fwd, with default
> settings I have the following error some often:
>
> 884.260394 [2950] netmap_transmit           igb1 from_host, drop packet
> size 2962 > 2048
>
> the only application which relies on host mode is bird, so those packets
> are probably from bird daemon, when I get those errors I get bird sessions
> failing and restart
>
> I raised dev.netmap.buf_size to 5000 it ajusted to 5120, things got better
> but I still have logs:
>
> netmap_transmit           igb1 from_host, drop packet size 5858 > 5120
>
> Now the main question is, when dev.netmap.buf_size is 2048 the application
> uses 1.3G of RAM but when I raise to 5120 it uses 3G of RAM.
>
> So I need to understand, is this packet size really related from what I get
> from the application packets coming from host to netmap? If so can I allow
> for bigger sizes, like 16k (lo0 mtu) without pre-alloc so much more RAM?
>
> thank you
>
> E. Meyer
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-- 
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 Prof. Luigi RIZZO, rizzo at iet.unipi.it  . Dip. di Ing. dell'Informazione
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