Re: [PATCH v3 net-next] net: introduce dev_set_forwarding()

Eric Dumazet
2013-11-04T07:10:42Z

On Mon, 2013-11-04 at 14:26 +0800, Herbert Xu wrote:

> Also if your scenario had all GRO candidates then not using
> frag_list would seem to be a bad workaround for an underlying
> latency problem. Rather than arbitrarily limiting the aggregation
> to 22K surely it would make more sense to limit it based on your
> actual latency requirements?

I have never limited GRO aggregation to 22K.

You did this in commit 81705ad1b2f926d
("gro: Do not merge paged packets into frag_list")

I exactly implemented what you suggested in your patch :

"In future we can optimise this further by doing frag_list merging
but making sure that we continue to fill in the page array."

Using frag_list for skb meant to be delivered to local stack is mostly
fine. Its for forwarding that its not a win, since no driver actually
supports frag_list and we revert to skb_segment().

So my latest patch about _not_ building fat skbs with frag_list on a
router makes sense.