On Fri, Jul 10, 2020 at 11:13 PM Sridhar Samudrala
<sridhar.samudrala@xxxxxxxxx> wrote:
>
> This patch triggers non-blocking busy poll when busy_poll is enabled,
> epoll is called with a timeout of 0 and is associated with a napi_id.
> This enables an app thread to go through napi poll routine once by
> calling epoll with a 0 timeout.
>
> poll/select with a 0 timeout behave in a similar manner.
>
> Signed-off-by: Sridhar Samudrala <sridhar.samudrala@xxxxxxxxx>
>
> v4:
> - Fix a typo (Andy)
> v3:
> - reset napi_id if no event available after busy poll (Alex)
> v2:
> - Added net_busy_loop_on() check (Eric)
> ---
> fs/eventpoll.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index 12eebcdea9c8..10da7a8e1c2b 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -1847,6 +1847,22 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
> eavail = ep_events_available(ep);
> write_unlock_irq(&ep->lock);
>
> + /*
> + * Trigger non-blocking busy poll if timeout is 0 and there are
> + * no events available. Passing timed_out(1) to ep_busy_loop
> + * will make sure that busy polling is triggered only once.
> + */
> + if (!eavail && net_busy_loop_on()) {
> + ep_busy_loop(ep, timed_out);
> +
> + write_lock_irq(&ep->lock);
> + eavail = ep_events_available(ep);
> + write_unlock_irq(&ep->lock);
> +
> + if (!eavail)
> + ep_reset_busy_poll_napi_id(ep);
> + }
> +
> goto send_events;
> }
>
This addresses the concern that I had.
Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
