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

Eric Dumazet
2013-10-30T04:16:19Z

On Wed, 2013-10-30 at 12:08 +0800, Herbert Xu wrote:
> On Tue, Oct 29, 2013 at 09:06:52PM -0700, Eric Dumazet wrote:
> >
> > I am not sure 64K GRO packets that must be segmented are going to be
> > faster than 22K packets without segmentation at all (TSO path on xmit)
>
> Indeed that is a tough call, but I think conceptually the 64K
> case is much nicer than a sysctl that gets magically turned off.

The thing is this only matters for hosts receiving at line rate on few
TCP flows.

A router should not build too big GRO packets, as it adds latencies.

Really, we had to make TSO packets being auto sized, lets not add the
syndrome again.

So I do not really understand David concern about emitting a warning.

If a machine is used as a router, building GRO packets of 17 MSS is
absolutely fine.