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

["Mattias Rönnblom" <mattias.ronnblom@ericsson.com>]

On 2023-05-11 09:09, Morten Brørup wrote:
>> From: Mattias Rönnblom [mailto:mattias.ronnblom@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@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.
> 

Yes, since it's a public header. Thanks.

>>   		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@smartsharesystems.com>
>