[dpdk-dev] No packets received if burst is too small in rte_eth_rx_burst

[tom.barbette at ulg.ac.be]

Hi,

Your comments made me saw the line "PMD: i40e_set_rx_function(): Vector rx enabled, please make sure RX burst size no less than 4 (port=0)."

The problem was probably that I was under this limit... Is there a way to get that limit through a function or something? 

With 16.04 I received sometimes 5 or 7 packets with a burst_size of 4 which respects this limit. I see that "[dpdk-dev] net/i40e: fix out-of-bounds writes during vector Rx" fixed that, as the limit was in fact 32 no matter the message.

At the end, what should be the minimal rx burst size? How to find it at runtime for any NIC? I imagine that vector rx will create a problem if I give a burst size of 1 even with a recent DPDK version, right?

Thanks,
Tom

Tom Barbette 
PhD Student @ Université de Liège 

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----- Mail original -----
De: "Bruce Richardson" <bruce.richardson at intel.com>
À: "tom barbette" <tom.barbette at ulg.ac.be>
Cc: dev at dpdk.org
Envoyé: Mercredi 14 Décembre 2016 17:52:21
Objet: Re: [dpdk-dev] No packets received if burst is too small in rte_eth_rx_burst

On Wed, Dec 14, 2016 at 04:13:53PM +0100, tom.barbette at ulg.ac.be wrote:
> Hi list,
> 
> Between 2.2.0 and 16.04 (up to at least 16.07.2 if not current), with the XL710 controller I do not get any packet when calling rte_eth_rx_burst if nb_pkts is too small. I would say smaller than 32. The input rate is not big, if that helps. But It should definitely get at least one packet per second.
> 
> Any ideas? Is that a bug or expected behaviour? Could be caused by other ABI changes?
> 
Does this issue still occur even if you disable the vector driver in
your build-time configuration?

/Bruce