From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id 571D3B368 for ; Thu, 31 Jul 2014 22:19:06 +0200 (CEST) Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga102.fm.intel.com with ESMTP; 31 Jul 2014 13:21:06 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,774,1400050800"; d="scan'208";a="578409942" Received: from unknown (HELO localhost.localdomain) ([134.134.172.151]) by fmsmga002.fm.intel.com with ESMTP; 31 Jul 2014 13:21:06 -0700 Date: Thu, 31 Jul 2014 13:19:50 -0700 From: Bruce Richardson To: Neil Horman Message-ID: <20140731201949.GA28495@localhost.localdomain> References: <1406665466-29654-1-git-send-email-nhorman@tuxdriver.com> <20140730210920.GB6420@localhost.localdomain> <20140731131351.GA20718@hmsreliant.think-freely.org> <5766264.li3nkTmgY6@xps13> <20140731143228.GB20718@hmsreliant.think-freely.org> <20140731181032.GC20718@hmsreliant.think-freely.org> <20140731183631.GC6420@localhost.localdomain> <20140731190117.GD20718@hmsreliant.think-freely.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140731190117.GD20718@hmsreliant.think-freely.org> Organization: Intel Shannon Limited. Registered in Ireland. Registered Office: Collinstown Industrial Park, Leixlip, County Kildare. Registered Number: 308263. Business address: Dromore House, East Park, Shannon, Co. Clare. User-Agent: Mutt/1.5.21 (2010-09-15) Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [PATCH 0/2] dpdk: Allow for dynamic enablement of some isolated features 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: Thu, 31 Jul 2014 20:19:06 -0000 On Thu, Jul 31, 2014 at 03:01:17PM -0400, Neil Horman wrote: > On Thu, Jul 31, 2014 at 11:36:32AM -0700, Bruce Richardson wrote: > > > > I think a good first step here that I can't see anyone objecting to is > > to enable the ixgbe driver to use the vector code path for a generic > > x86_64 build. I've run a quick test here, and changing "_mm_popcnt_u64" > > to "__builtin_popcountll" [and the include from nmmintrin to tmmintrin] > > allows a compile for machine type default, and testpmd can still forward > > packets at a good rate (roughly perf down about 10% vs native compile on > > SNB). > > The ACL is a tougher nut to crack, but anyone see any issues with that > > two-line change to ixgbe_rxtx_vec.c? [Neil, since you started the patch > > set thread, do you want to submit an official patch here, or would you prefer I > > do so?] > > > > I'm happy to do so, Though 10% performance degradation vs. using the sse4.2 > instructions in that path seems significant, isn't it? Given that performance > delta, it seems like it would still be preferable to have a path that used the > sse4.2 instructions when they're available. Or am I misreading what you mean > when you say down 10% > > Neil > Ok, I did a little bit more testing here. Using the vector pmd compiled for generic x86_64 and using __builtin_popcountll is approx 35% faster for packet IO than the existing fast-path functions. It is also 7% (a bit lower than ~10% as I originally stated) slower than the existing native-compiled vpmd on a Sandy Bridge platform. I then ran an extra test, using EXTRA_CFLAGS='-msse4.2' to turn on the extra instructions. The ~7% performance drop went to ~3%, so we would gain a little more with using SSE4.2, but compared to the gain from having the vector driver at all, it's not that much. [I don't have a system handy with AVX2 support to see what boosts might come from compiling with that instruction set enabled.] Because of this, I'd take the ~35% speed boost for now, and try and find what would be the best general way to solve this problem across all libraries. Also, I think that anyone who needs that extra 4% performance probably wants the other 3% too, and so will compile up the code from source using the "native" compilation target. :-) /Bruce