[PATCH] eventdev: avoid non-burst shortcut for variable-size bursts

[Morten Brørup]

> From: Mattias Rönnblom [mailto:mattias.ronnblom at ericsson.com]
> Sent: Thursday, 11 May 2023 08.43
> 
> Use non-burst event enqueue and dequeue calls from burst enqueue and
> dequeue only when the burst size is compile-time constant (and equal
> to one).
> 
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> ---
>  lib/eventdev/rte_eventdev.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/eventdev/rte_eventdev.h b/lib/eventdev/rte_eventdev.h
> index a90e23ac8b..8af15816db 100644
> --- a/lib/eventdev/rte_eventdev.h
> +++ b/lib/eventdev/rte_eventdev.h
> @@ -1944,7 +1944,7 @@ __rte_event_enqueue_burst(uint8_t dev_id, uint8_t
> port_id,
>  	 * Allow zero cost non burst mode routine invocation if application
>  	 * requests nb_events as const one
>  	 */
> -	if (nb_events == 1)
> +	if (__builtin_constant_p(nb_events) && nb_events == 1)

In my experience using __builtin_constant_p(), you need __extension__(__builtin_constant_p(nb_events)) to avoid warnings about using this non-standard feature.

>  		return (fp_ops->enqueue)(port, ev);
>  	else
>  		return fn(port, ev, nb_events);
> @@ -2200,7 +2200,7 @@ rte_event_dequeue_burst(uint8_t dev_id, uint8_t port_id,
> struct rte_event ev[],
>  	 * Allow zero cost non burst mode routine invocation if application
>  	 * requests nb_events as const one
>  	 */
> -	if (nb_events == 1)
> +	if (__builtin_constant_p(nb_events) && nb_events == 1)
>  		return (fp_ops->dequeue)(port, ev, timeout_ticks);
>  	else
>  		return (fp_ops->dequeue_burst)(port, ev, nb_events,
> --
> 2.34.1

With __extension__() added,

Acked-by: Morten Brørup <mb at smartsharesystems.com>