From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by dpdk.org (Postfix) with ESMTP id B9B621B7B7 for ; Wed, 25 Oct 2017 22:16:18 +0200 (CEST) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Oct 2017 13:16:17 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,433,1503385200"; d="scan'208";a="327710176" Received: from bricha3-mobl3.ger.corp.intel.com ([10.252.7.122]) by fmsmga004.fm.intel.com with SMTP; 25 Oct 2017 13:16:15 -0700 Received: by (sSMTP sendmail emulation); Wed, 25 Oct 2017 21:16:14 +0100 Date: Wed, 25 Oct 2017 21:16:14 +0100 From: Bruce Richardson To: Ferruh Yigit Cc: "Roger B. Melton" , wenzhuo.lu@intel.com, dev@dpdk.org, "Ananyev, Konstantin" Message-ID: <20171025201614.GA12968@bricha3-MOBL3.ger.corp.intel.com> References: <20171012172435.34700-1-rmelton@cisco.com> <1e8e5766-6c52-d09d-d7ac-11492b946c90@intel.com> <3b4d34fa-309e-10d4-e992-3d82034e4c41@cisco.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Research and Development Ireland Ltd. User-Agent: Mutt/1.9.1 (2017-09-22) Subject: Re: [dpdk-dev] [PATCH v2] net/e1000: correct VLAN tag byte order for i35x LB packets 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: Wed, 25 Oct 2017 20:16:19 -0000 On Wed, Oct 25, 2017 at 11:11:08AM -0700, Ferruh Yigit wrote: > On 10/23/2017 10:42 AM, Roger B. Melton wrote: > > On 10/20/17 3:04 PM, Ferruh Yigit wrote: > >> On 10/12/2017 10:24 AM, Roger B Melton wrote: > >>> When copying VLAN tags from the RX descriptor to the vlan_tci field > >>> in the mbuf header, igb_rxtx.c:eth_igb_recv_pkts() and > >>> eth_igb_recv_scattered_pkts() both assume that the VLAN tag is always > >>> little endian. While i350, i354 and /i350vf VLAN non-loopback > >>> packets are stored little endian, VLAN tags in loopback packets for > >>> those devices are big endian. > >>> > >>> For i350, i354 and i350vf VLAN loopback packets, swap the tag when > >>> copying from the RX descriptor to the mbuf header. This will ensure > >>> that the mbuf vlan_tci is always little endian. > >>> > >>> Signed-off-by: Roger B Melton > >> <...> > >> > >>> @@ -946,9 +954,16 @@ eth_igb_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, > >>> > >>> rxm->hash.rss = rxd.wb.lower.hi_dword.rss; > >>> hlen_type_rss = rte_le_to_cpu_32(rxd.wb.lower.lo_dword.data); > >>> - /* Only valid if PKT_RX_VLAN_PKT set in pkt_flags */ > >>> - rxm->vlan_tci = rte_le_to_cpu_16(rxd.wb.upper.vlan); > >>> - > >>> + /* > >>> + * The vlan_tci field is only valid when PKT_RX_VLAN_PKT is > >>> + * set in the pkt_flags field and must be in CPU byte order. > >>> + */ > >>> + if ((staterr & rte_cpu_to_le_32(E1000_RXDEXT_STATERR_LB)) && > >>> + (rxq->flags & IGB_RXQ_FLAG_LB_BSWAP_VLAN)) { > >> This is adding more condition checks into Rx path. > >> What is the performance cost of this addition? > > > > I have not measured the performance cost, but I can collect data. What > > specifically are you looking for? > > > > To be clear the current implementation incorrect as it does not > > normalize the vlan tag to CPU byte order before copying it into mbuf and > > applications have no visibility to determine if the tag in the mbuf is > > big or little endian. > > > > Do you have any suggestions for an alternative approach to avoid rx > > patch checks? > > No suggestion indeed. And correctness matters. > > But this add a cost and I wonder how much it is, based on that result it may be > possible to do more investigation for alternate solutions or trade-offs. > > Konstantin, Bruce, Wenzhuo, > > What do you think, do you have any comment? > For a 1G driver, is performance really that big an issue? Unless you have a *lot* of 1G ports, I would expect most platforms not to notice an extra couple of cycles when dealing with 1G line rates. /Bruce