From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 84B585A1F for ; Mon, 7 Sep 2015 16:41:07 +0200 (CEST) Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP; 07 Sep 2015 07:41:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,485,1437462000"; d="scan'208";a="800072366" Received: from irsmsx108.ger.corp.intel.com ([163.33.3.3]) by fmsmga002.fm.intel.com with ESMTP; 07 Sep 2015 07:41:06 -0700 Received: from irsmsx103.ger.corp.intel.com ([169.254.3.251]) by IRSMSX108.ger.corp.intel.com ([169.254.11.12]) with mapi id 14.03.0224.002; Mon, 7 Sep 2015 15:41:04 +0100 From: "Richardson, Bruce" To: Zoltan Kiss , "dev@dpdk.org" Thread-Topic: [PATCH] ixgbe: prefetch packet headers in vector PMD receive function Thread-Index: AQHQ5Orfy1XDbo4m6UqzmyFGbLUN4J4w9hQAgAAYzeCAAAXNgIAAF6+Q Date: Mon, 7 Sep 2015 14:41:04 +0000 Message-ID: <59AF69C657FD0841A61C55336867B5B035922A83@IRSMSX103.ger.corp.intel.com> References: <1441135036-7491-1-git-send-email-zoltan.kiss@linaro.org> <55ED8252.1020900@linaro.org> <59AF69C657FD0841A61C55336867B5B0359227DF@IRSMSX103.ger.corp.intel.com> <55ED9BFD.7040009@linaro.org> In-Reply-To: <55ED9BFD.7040009@linaro.org> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.180] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH] ixgbe: prefetch packet headers in vector PMD receive function X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Sep 2015 14:41:07 -0000 > -----Original Message----- > From: Zoltan Kiss [mailto:zoltan.kiss@linaro.org] > Sent: Monday, September 7, 2015 3:15 PM > To: Richardson, Bruce; dev@dpdk.org > Cc: Ananyev, Konstantin > Subject: Re: [PATCH] ixgbe: prefetch packet headers in vector PMD receive > function >=20 >=20 >=20 > On 07/09/15 13:57, Richardson, Bruce wrote: > > > > > >> -----Original Message----- > >> From: Zoltan Kiss [mailto:zoltan.kiss@linaro.org] > >> Sent: Monday, September 7, 2015 1:26 PM > >> To: dev@dpdk.org > >> Cc: Ananyev, Konstantin; Richardson, Bruce > >> Subject: Re: [PATCH] ixgbe: prefetch packet headers in vector PMD > >> receive function > >> > >> Hi, > >> > >> I just realized I've missed the "[PATCH]" tag from the subject. Did > >> anyone had time to review this? > >> > > > > Hi Zoltan, > > > > the big thing that concerns me with this is the addition of new > > instructions for each packet in the fast path. Ideally, this > > prefetching would be better handled in the application itself, as for > > some apps, e.g. those using pipelining, the core doing the RX from the > > NIC may not touch the packet data at all, and the prefetches will > instead cause a performance slowdown. > > > > Is it possible to get the same performance increase - or something > > close to it - by making changes in OVS? >=20 > OVS already does a prefetch when it's processing the previous packet, but > apparently it's not early enough. At least for my test scenario, where I'= m > forwarding UDP packets with the least possible overhead. I guess in tests > where OVS does more complex processing it should be fine. > I'll try to move the prefetch earlier in OVS codebase, but I'm not sure i= f > it'll help. I would suggest trying to prefetch more than one packet ahead. Prefetching = 4 or 8 ahead might work better, depending on the processing being done. /Bruce