[dpdk-dev] Requirement of minimum Rx burst size for PMDs

[Yongseok Koh]

On Fri, Oct 20, 2017 at 03:23:10PM +0300, Andrew Rybchenko wrote:
> On 10/20/2017 02:58 PM, Bruce Richardson wrote:
> > On Fri, Oct 20, 2017 at 01:07:17PM +0300, Andrew Rybchenko wrote:
> > > On 10/20/2017 04:18 AM, Yongseok Koh wrote:
> > > > Therefore, how about adding min_rx/tx_burst_sz in struct rte_eth_dev_info and
> > > > have PMDs fill it in on dev_ops->dev_infos_get() so as to make apps comply with
> > > > it.
> > > Just for my understand, what should happen if application wants to send only
> > > one packet? 5 packets? 33? 35?
> > I actually think there is a mistake in the original mails. At least for
> > Intel PMDs there is no restriction on min TX burst sizes in any code
> > path. The vector RX on the other hand does require a minimum number of empty
> > buffers to be passed to it, so you need to request no fewer than 4
> > packets in a burst. If only one packet is available that will still be
> > returned to you, but you must request at least 4
> 
> I see. The thread subject says Rx, but Tx (min_tx_burst_sz) is mentioned
> above.
> If Tx is mentioned by mistake, it is clear now.

Oops, Tx was mistakenly mentioned. Neither Intel nor Mellanox PMD has such
restriction on Tx burst size.

Will come up with a patch for it soon.

Thanks,
Yongseok