On Wed, Nov 25, 2020 at 7:49 AM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
>
> Modify the tx writeable condition from the queue is not full to the
> number of present tx queues is less than the half of the total number
> of queues. Because the tx queue not full is a very short time, this will
> cause a large number of EPOLLOUT events, and cause a large number of
> process wake up.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Thank you Xuan!
Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> ---
> net/xdp/xsk.c | 16 +++++++++++++---
> net/xdp/xsk_queue.h | 6 ++++++
> 2 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 0df8651..22e35e9 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -211,6 +211,14 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len,
> return 0;
> }
>
> +static bool xsk_tx_writeable(struct xdp_sock *xs)
> +{
> + if (xskq_cons_present_entries(xs->tx) > xs->tx->nentries / 2)
> + return false;
> +
> + return true;
> +}
> +
> static bool xsk_is_bound(struct xdp_sock *xs)
> {
> if (READ_ONCE(xs->state) == XSK_BOUND) {
> @@ -296,7 +304,8 @@ void xsk_tx_release(struct xsk_buff_pool *pool)
> rcu_read_lock();
> list_for_each_entry_rcu(xs, &pool->xsk_tx_list, tx_list) {
> __xskq_cons_release(xs->tx);
> - xs->sk.sk_write_space(&xs->sk);
> + if (xsk_tx_writeable(xs))
> + xs->sk.sk_write_space(&xs->sk);
> }
> rcu_read_unlock();
> }
> @@ -499,7 +508,8 @@ static int xsk_generic_xmit(struct sock *sk)
>
> out:
> if (sent_frame)
> - sk->sk_write_space(sk);
> + if (xsk_tx_writeable(xs))
> + sk->sk_write_space(sk);
>
> mutex_unlock(&xs->mutex);
> return err;
> @@ -556,7 +566,7 @@ static __poll_t xsk_poll(struct file *file, struct socket *sock,
>
> if (xs->rx && !xskq_prod_is_empty(xs->rx))
> mask |= EPOLLIN | EPOLLRDNORM;
> - if (xs->tx && !xskq_cons_is_full(xs->tx))
> + if (xs->tx && xsk_tx_writeable(xs))
> mask |= EPOLLOUT | EPOLLWRNORM;
>
> return mask;
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> index b936c46..b655004 100644
> --- a/net/xdp/xsk_queue.h
> +++ b/net/xdp/xsk_queue.h
> @@ -307,6 +307,12 @@ static inline bool xskq_cons_is_full(struct xsk_queue *q)
> q->nentries;
> }
>
> +static inline __u64 xskq_cons_present_entries(struct xsk_queue *q)
> +{
> + /* No barriers needed since data is not accessed */
> + return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer);
> +}
> +
> /* Functions for producers */
>
> static inline u32 xskq_prod_nb_free(struct xsk_queue *q, u32 max)
> --
> 1.8.3.1
>
