Re: [PATCH net-next v3 2/3] xsk: use atomic operations around cached_prod for copy mode

[Paolo Abeni <pabeni@redhat.com>]

On 11/28/25 2:46 PM, Jason Xing wrote:
> From: Jason Xing <kernelxing@tencent.com>
> 
> Use atomic_try_cmpxchg operations to replace spin lock. Technically
> CAS (Compare And Swap) is better than a coarse way like spin-lock
> especially when we only need to perform a few simple operations.
> Similar idea can also be found in the recent commit 100dfa74cad9
> ("net: dev_queue_xmit() llist adoption") that implements the lockless
> logic with the help of try_cmpxchg.
> 
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> ---
> Paolo, sorry that I didn't try to move the lock to struct xsk_queue
> because after investigation I reckon try_cmpxchg can add less overhead
> when multiple xsks contend at this point. So I hope this approach
> can be adopted.

I still think that moving the lock would be preferable, because it makes
sense also from a maintenance perspective. Can you report the difference
you measure atomics vs moving the spin lock?

Have you tried moving cq_prod_lock, too?

/P