[Codel] fq_codel_drop vs a udp flood

Eric Dumazet eric.dumazet at gmail.com
Fri May 6 11:58:34 EDT 2016

On Fri, 2016-05-06 at 17:25 +0200, moeller0 wrote:
> Hi Eric,
> > On May 6, 2016, at 15:25 , Eric Dumazet <eric.dumazet at gmail.com> wrote:

> > Angles of attack :
> > 
> > 1) I will provide a per device /sys/class/net/eth0/gro_max_frags so that
> > we can more easily control amount of segs per GRO packets. It makes
> > sense to have GRO, but not so much allowing it to cook big packets that
> > might hurt FQ.
> 	This sounds great, so we can teach, say sqm to set this to a
> reasonable value given the (shaped) bandwidth of a given interface.
> Would something like this also make sense/is possible on the send side
> for GSO/TSO?

Problem of doing this on the send side, is that too big GRO packets
would need to be segmented _before_ reaching qdisc, and we do not have
such support. (The segmentation happens after qdisc before hitting

In any case, that would be more cpu cycles. It is probably better to
control GRO sizes to optimal values.

I posted the fq_codel patch to netdev :


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