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

Andrew Rybchenko arybchenko at solarflare.com
Fri Oct 20 14:23:10 CEST 2017


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.

Andrew.


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