From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 3A2C6F6D2 for ; Mon, 19 Dec 2016 11:25:07 +0100 (CET) Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga101.jf.intel.com with ESMTP; 19 Dec 2016 02:25:07 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,373,1477983600"; d="scan'208";a="799940950" Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.221.64]) by FMSMGA003.fm.intel.com with SMTP; 19 Dec 2016 02:25:05 -0800 Received: by (sSMTP sendmail emulation); Mon, 19 Dec 2016 10:25:04 +0000 Date: Mon, 19 Dec 2016 10:25:04 +0000 From: Bruce Richardson To: tom.barbette@ulg.ac.be Cc: dev@dpdk.org Message-ID: <20161219102504.GA170848@bricha3-MOBL3.ger.corp.intel.com> References: <415214732.17903310.1481728244157.JavaMail.zimbra@ulg.ac.be> <597694261.17905196.1481728433903.JavaMail.zimbra@ulg.ac.be> <20161214165220.GC110884@bricha3-MOBL3.ger.corp.intel.com> <1289578237.19546607.1481971405418.JavaMail.zimbra@ulg.ac.be> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1289578237.19546607.1481971405418.JavaMail.zimbra@ulg.ac.be> Organization: Intel Research and =?iso-8859-1?Q?De=ACvel?= =?iso-8859-1?Q?opment?= Ireland Ltd. User-Agent: Mutt/1.7.1 (2016-10-04) Subject: Re: [dpdk-dev] No packets received if burst is too small in rte_eth_rx_burst X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 19 Dec 2016 10:25:08 -0000 On Sat, Dec 17, 2016 at 11:43:25AM +0100, tom.barbette@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" > À: "tom barbette" > 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.barbette@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