From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id A8DB5374F for ; Wed, 21 Sep 2016 04:40:37 +0200 (CEST) Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga104.jf.intel.com with ESMTP; 20 Sep 2016 19:40:36 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,371,1470726000"; d="scan'208";a="11979494" Received: from yliu-dev.sh.intel.com (HELO yliu-dev) ([10.239.67.162]) by orsmga004.jf.intel.com with ESMTP; 20 Sep 2016 19:40:35 -0700 Date: Wed, 21 Sep 2016 10:41:13 +0800 From: Yuanhan Liu To: Maxime Coquelin Cc: huawei.xie@intel.com, dev@dpdk.org, vkaplans@redhat.com, mst@redhat.com Message-ID: <20160921024113.GB23158@yliu-dev.sh.intel.com> References: <1468333932-26509-1-git-send-email-maxime.coquelin@redhat.com> <20160803140305.GD30752@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) Subject: Re: [dpdk-dev] [RFC] vhost: Add indirect descriptors support to the TX path 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, 21 Sep 2016 02:40:38 -0000 On Fri, Aug 05, 2016 at 02:18:42PM +0200, Maxime Coquelin wrote: > > > On 08/03/2016 04:03 PM, Yuanhan Liu wrote: > >On Tue, Jul 12, 2016 at 04:32:12PM +0200, Maxime Coquelin wrote: > >>Indirect descriptors are usually supported by virtio-net devices, > >>allowing to dispatch a large number of large requests. > >> > >>When the virtio device sends a packet using indirect descriptors, > >>only one slot is used in the ring, even for large packets. > >> > >>Signed-off-by: Maxime Coquelin > >>--- > >>I have a two questions regarding the implementation of this feature: > >> > >>1. Should I add a check to ensure the indirect feature is supported > >>(i.e. the negociation succeeded) when having an indirect desc? > >> > >>2. Should I check in copy_desc_to_mbuf() that we don't have a nested > >>indirect descriptor? > >> > >>Both these sanity checks are recommended from the virtio spec, but > >>since it is to be done in the hot path, it may introduce some > >>performance penalties. > >> > >>Note that the first check is not done in the Kernel vhost driver, whereas > >>the second one is. > > > >I think we could firstly follow the Linux kernel implementation. > OK, I can do that in the v2. FYI, I'm waiting for it. --yliu