Re: [PATCH v2 net-next] net: introduce gro_frag_list_enable sysctl

Eric Dumazet
2013-11-02T18:28:29Z

On Sat, 2013-11-02 at 21:43 +0400, Oleg A.Arkhangelsky wrote:
>
> 30.10.2013, 06:33, "David Miller" <davem@davemloft.net>:
>
> > GRO should always win, even on a router, because it decreases the
> > number of fundamental operations (routing lookups) that the stack
> > needs to perform.
>
> Yes, unless the case when you're using Linux as IP router which is
> forwarding 500K mixed IP (TCP and UDP) flows traffic @ 10-20 Gbit/s.
> Then GRO is unnecessarily overhead, cause there's no possibility to
> accumulate adequate GRO list in such scenario.
>

This was assuming the aggregation factor was not 0.

Even with 500K flows, you can have typically bursts of two packets per
flow.

Thats one of the reason why I chose to default
/proc/sys/net/ipv4/tcp_min_tso_segs to 2