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 68EB09410 for ; Wed, 27 Jan 2016 07:35:35 +0100 (CET) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP; 26 Jan 2016 22:35:34 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,354,1449561600"; d="scan'208";a="36879559" Received: from yliu-dev.sh.intel.com (HELO yliu-dev) ([10.239.66.49]) by fmsmga004.fm.intel.com with ESMTP; 26 Jan 2016 22:35:33 -0800 Date: Wed, 27 Jan 2016 14:35:58 +0800 From: Yuanhan Liu To: "Xie, Huawei" Message-ID: <20160127063558.GI4257@yliu-dev.sh.intel.com> References: <1449122773-25510-1-git-send-email-yuanhan.liu@linux.intel.com> <1449122773-25510-5-git-send-email-yuanhan.liu@linux.intel.com> <20160127032245.GB4257@yliu-dev.sh.intel.com> <20160127060236.GG4257@yliu-dev.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Cc: "dev@dpdk.org" , Victor Kaplansky , "Michael S. Tsirkin" Subject: Re: [dpdk-dev] [PATCH 4/5] vhost: do not use rte_memcpy for virtio_hdr copy 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: Wed, 27 Jan 2016 06:35:35 -0000 On Wed, Jan 27, 2016 at 06:16:37AM +0000, Xie, Huawei wrote: > On 1/27/2016 2:02 PM, Yuanhan Liu wrote: > > On Wed, Jan 27, 2016 at 05:56:56AM +0000, Xie, Huawei wrote: > >> On 1/27/2016 11:22 AM, Yuanhan Liu wrote: > >>> On Wed, Jan 27, 2016 at 02:46:39AM +0000, Xie, Huawei wrote: > >>>> On 12/3/2015 2:03 PM, Yuanhan Liu wrote: > >>>>> + if (vq->vhost_hlen == sizeof(struct virtio_net_hdr_mrg_rxbuf)) { > >>>>> + *(struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr = hdr; > >>>>> + } else { > >>>>> + *(struct virtio_net_hdr *)(uintptr_t)desc_addr = hdr.hdr; > >>>>> + } > >>>> Thanks! > >>>> We might simplify this further. Just reset the first two fields flags > >>>> and gso_type. > >>> What's this "simplification" for? Don't even to say that we will add > >>> TSO support, which modifies few more files, such as csum_start: reseting > >>> the first two fields only is wrong here. > >> I know TSO before commenting, but at least in this implementation and > >> this specific patch, i guess zeroing two fields are enough. > >> > >> What is wrong resetting only two fields? > > I then have to ask "What is the benifit of resetting only two fields"? > > If doing so, we have to change it back for TSO. My proposal requires no > > extra change when adding TSO support. > > ? Benefit is we save four unnecessary stores. Hmm..., the hdr size is 12 bytes at most. I mean, does it really matter, coping 3 bytes, or coping 12 bytes in a row? --yliu