On Wed, 2016-12-07 at 17:09 +0000, David Laight wrote:
> From: Paolo Abeni
> > Sent: 06 December 2016 17:08
> ...
> > @@ -79,6 +82,9 @@ struct udp_sock {
> > int (*gro_complete)(struct sock *sk,
> > struct sk_buff *skb,
> > int nhoff);
> > +
> > + /* since we are prone to drops, avoid dirtying any sk cacheline */
> > + atomic_t drops ____cacheline_aligned_in_smp;
> > };
>
> Isn't that likely to create a large hole on systems with large cache lines.
> (Same as any other use of ____cacheline_aligned_in_smp.)
Yes, I would like to avoid that, unless we come to the conclusion it is
absolutely needed.
I feel that we could simply use a pointer, and allocate memory on
demand, since many sockets do not ever experience a drop.
The pointer could stay in a read mostly section.
We even could use per cpu or node counter for some heavy drop cases.
