Re: [PATCH net-next v10 11/14] tcp: RX path for devmem TCP

Paolo Abeni
2024-06-04T10:53:42Z

On Thu, 2024-05-30 at 20:16 +0000, Mina Almasry wrote:
> @@ -2317,6 +2318,213 @@ static int tcp_inq_hint(struct sock *sk)
> return inq;
> }
>
> +/* batch __xa_alloc() calls and reduce xa_lock()/xa_unlock() overhead. */
> +struct tcp_xa_pool {
> + u8 max; /* max <= MAX_SKB_FRAGS */
> + u8 idx; /* idx <= max */
> + __u32 tokens[MAX_SKB_FRAGS];
> + netmem_ref netmems[MAX_SKB_FRAGS];
> +};
> +
> +static void tcp_xa_pool_commit(struct sock *sk, struct tcp_xa_pool *p,
> + bool lock)
> +{
> + int i;
> +
> + if (!p->max)
> + return;
> + if (lock)
> + xa_lock_bh(&sk->sk_user_frags);

The conditional lock here confuses sparse.

I think you can avoid it providing a unlocked version (no need to check
for '!p->max' the only caller wanting the unlocked version already
performs such check) and a locked one, calling the other.

Cheers,

Paolo