Re: [dpdk-dev] [PATCH] net/virtio: remove handling of zero desc number on RxQ setup

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 9/14/21 8:40 AM, Andrew Rybchenko wrote:
> On 9/13/21 10:25 PM, Maxime Coquelin wrote:
>>
>>
>> On 8/20/21 2:47 PM, Andrew Rybchenko wrote:
>>> From: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
>>>
>>> Rx queue setup callback allows to use the whole ring when
>>> descriptor number argument equals zero. There's no point to
>>> handle zero in any way since RTE Rx queue setup function
>>> rte_eth_rx_queue_setup() doesn't pass zero using fallback
>>> values.
>>>
>>> Fixes: 3be82f5cc5e3 ("ethdev: support PMD-tuned Tx/Rx parameters")
>>> Cc: stable@dpdk.org
>>>
>>> Signed-off-by: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
>>> Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>> ---
>>>  drivers/net/virtio/virtio_rxtx.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
>>> index 8a48fba5cc..18f03c9fc9 100644
>>> --- a/drivers/net/virtio/virtio_rxtx.c
>>> +++ b/drivers/net/virtio/virtio_rxtx.c
>>> @@ -706,7 +706,7 @@ virtio_dev_rx_queue_setup(struct rte_eth_dev *dev,
>>>  	}
>>>  	vq->vq_free_thresh = rx_free_thresh;
>>>  
>>> -	if (nb_desc == 0 || nb_desc > vq->vq_nentries)
>>> +	if (nb_desc > vq->vq_nentries)
>>>  		nb_desc = vq->vq_nentries;
>>>  	vq->vq_free_cnt = RTE_MIN(vq->vq_free_cnt, nb_desc);
>>>  
>>>
>>
>> Is that really a fix?
>> I see it more like an optimization in a cold path, so maybe it is not
>> worth backporting?
> 
> The main idea is not an optimization, but simplification of
> the code to make it easier to understand. Less special
> cases is better.
> 
> I agree that it does not make sense to backport it.

Ok, thanks. I'll will remove the Fixes tag while applying, no need to
resubmit.

Maxime
> 
>> Other than that:
>> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> 
> Thanks,
> Andrew.
>