On Sat, Dec 17, 2016 at 11:43:25AM +0100, tom.barbe...@ulg.ac.be wrote: > 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? >
Sadly, there doesn't appear to be any way to discover this, and the i40e driver requires at least a burst size of 4 even with the latest DPDK. >From i40e_rxtx_vec_sse.c: 243 /* nb_pkts has to be floor-aligned to RTE_I40E_DESCS_PER_LOOP */ 244 nb_pkts = RTE_ALIGN_FLOOR(nb_pkts, RTE_I40E_DESCS_PER_LOOP); 245 I think in this case the gap is not so much having a discovery mechanism to determine min burst size, but rather a driver gap so as to allow some form of slower-path fallback when we get below min-size bursts for the vector driver. /Bruce > Thanks, > Tom > > Tom Barbette > PhD Student @ Université de Liège > > Office 1/13 > Bâtiment B37 > Quartier Polytech > Allée de la découverte, 12 > 4000 Liège > > 04/366 91 75 > 0479/60 94 63 > > > ----- Mail original ----- > De: "Bruce Richardson" <bruce.richard...@intel.com> > À: "tom barbette" <tom.barbe...@ulg.ac.be> > Cc: dev@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.barbe...@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
