Hi,
Adding Willem, I think he can be interested.
On Fri, 2018-11-09 at 14:21 +0800, Li RongQing wrote:
> GRO for UDP needs to lookup socket twice, first is in gro receive,
> second is gro complete, so if store sock to skb to avoid looking up
> twice, this can give small performance boost
>
> netperf -t UDP_RR -l 10
>
> Before:
> Rate per sec: 28746.01
> After:
> Rate per sec: 29401.67
>
> Signed-off-by: Li RongQing <lirongq...@baidu.com>
> ---
> net/ipv4/udp_offload.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 0646d61f4fa8..429570112a33 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -408,6 +408,11 @@ struct sk_buff *udp_gro_receive(struct list_head *head,
> struct sk_buff *skb,
>
> if (udp_sk(sk)->gro_enabled) {
> pp = call_gro_receive(udp_gro_receive_segment, head, skb);
> +
> + if (!IS_ERR(pp) && NAPI_GRO_CB(pp)->count > 1) {
> + sock_hold(sk);
> + pp->sk = sk;
> + }
> rcu_read_unlock();
> return pp;
> }
What if 'pp' is NULL?
Aside from that, this replace a lookup with 2 atomic ops, and only when
such lookup is amortized on multiple aggregated packets: I'm unsure if
it's worthy and I don't understand how that improves RR tests (where
the socket can't see multiple, consecutive skbs, AFAIK).
Cheers,
Paolo
