From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id ED11EA0588; Thu, 16 Apr 2020 02:29:15 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 75EC81DA4F; Thu, 16 Apr 2020 02:29:15 +0200 (CEST) Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id ED8EF1DA4C for ; Thu, 16 Apr 2020 02:29:13 +0200 (CEST) IronPort-SDR: nFJ19Bw+ZK9giuKl4YSHJKa/hNtZMSPj0RIzLWvozt6qqA3xcYazj5Ww86/17paaDVe2gFtYOK cbaz1pXF4enw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2020 17:29:12 -0700 IronPort-SDR: UmbHTo88LsTWi1QpcOvsL63LWaZCB7n2rN4YY5A8lg8JuhKO5ylxvWAZueduPFjSPtcmNsSOdO V9rAP3/3eIAg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,388,1580803200"; d="scan'208";a="332665154" Received: from fmsmsx103.amr.corp.intel.com ([10.18.124.201]) by orsmga001.jf.intel.com with ESMTP; 15 Apr 2020 17:29:12 -0700 Received: from fmsmsx124.amr.corp.intel.com (10.18.125.39) by FMSMSX103.amr.corp.intel.com (10.18.124.201) with Microsoft SMTP Server (TLS) id 14.3.439.0; Wed, 15 Apr 2020 17:29:12 -0700 Received: from shsmsx152.ccr.corp.intel.com (10.239.6.52) by fmsmsx124.amr.corp.intel.com (10.18.125.39) with Microsoft SMTP Server (TLS) id 14.3.439.0; Wed, 15 Apr 2020 17:29:11 -0700 Received: from shsmsx103.ccr.corp.intel.com ([169.254.4.146]) by SHSMSX152.ccr.corp.intel.com ([169.254.6.209]) with mapi id 14.03.0439.000; Thu, 16 Apr 2020 08:29:09 +0800 From: "Liu, Yong" To: Maxime Coquelin , "Ye, Xiaolong" , "Wang, Zhihong" , "eperezma@redhat.com" CC: "dev@dpdk.org" Thread-Topic: [PATCH] vhost: remove deferred shadow update Thread-Index: AQHWCCz0NVLTzMDwtkaaCNuZzDJ9nqh5yi2AgACMkXD//4DugIABH7ew Date: Thu, 16 Apr 2020 00:29:08 +0000 Message-ID: <86228AFD5BCD8E4EBFD2B90117B5E81E63537285@SHSMSX103.ccr.corp.intel.com> References: <20200401212926.74989-1-yong.liu@intel.com> <86228AFD5BCD8E4EBFD2B90117B5E81E63536963@SHSMSX103.ccr.corp.intel.com> <5bd2477a-db3b-8179-470b-591ca37d93ad@redhat.com> In-Reply-To: <5bd2477a-db3b-8179-470b-591ca37d93ad@redhat.com> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-version: 11.2.0.6 dlp-reaction: no-action x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH] vhost: remove deferred shadow update 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: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > -----Original Message----- > From: Maxime Coquelin > Sent: Wednesday, April 15, 2020 11:04 PM > To: Liu, Yong ; Ye, Xiaolong ; > Wang, Zhihong ; eperezma@redhat.com > Cc: dev@dpdk.org > Subject: Re: [PATCH] vhost: remove deferred shadow update >=20 > Hi Marvin, >=20 > On 4/15/20 4:55 PM, Liu, Yong wrote: > > > > > >> -----Original Message----- > >> From: Maxime Coquelin > >> Sent: Wednesday, April 15, 2020 10:16 PM > >> To: Liu, Yong ; Ye, Xiaolong > ; > >> Wang, Zhihong ; eperezma@redhat.com > >> Cc: dev@dpdk.org > >> Subject: Re: [PATCH] vhost: remove deferred shadow update > >> > >> > >> > >> On 4/1/20 11:29 PM, Marvin Liu wrote: > >>> Defer shadow ring update will help overall throughput when frontend > >>> much slower than backend. But that is not all the cases we faced now. > >>> In case like ovs-dpdk + dpdk virtio user, frontend will much faster > >>> than backend. Frontend may not be able to collect available descs > when > >>> shadow update is deferred. Thus will harm RFC2544 performance. > >> > >> I don't understand this comment. What is the difference in term of > >> performance between Qemu + Virtio PMD and Virtio-User PMD, as the > >> datapath is the same? > >> > > > > Hi Maxime, > > The statement is for the different situations between virtio-net + vhos= t > pmd and virtio-user + vhost pmd in ovs. > > When combination is virtio-user + vhost pmd in ovs, frontend will be > much faster than backend. Defer used ring update won't give benefit when > requiring zero packet loss. >=20 > Ok, so you mean Virtio PMD vs. Virtio-net kernel driver. >=20 > Regarding who is faster between Virtio PMD and Vhost PMD, it actually > depends on what the applications using them are doing. >=20 > If you have OVS on host + testpmd on guest doing IO fowarding, then of > course the frontent is much faster. >=20 > But if you have testpmd IO forward on host + tespmd MACSWAP forward in > guest, then the frontend could be slower. >=20 > That looks like a benchmark optimization only. >=20 Maxime, IMHO, it will be more like performance bug fix. Defer shadow ring update me= thod brings performance issue in certain case. Thanks, Marvin > > Regards, > > Marvin > > > >>> Solution is just remove deferred shadow update, which will help > RFC2544 > >>> and fix potential issue with virtio net driver. > >> > >> What is the potential issue? > >> > >> Maxime > > > > It is napi stops issue which has been fixed by Eugenio. >=20 > OK, then I would suggest to change the patch title to: > "vhost: fix shadow update" >=20 > Then explicit the commit message to point to Eugenio's bug, and tag it > with the proper Fixes tag, so that the patch gets backported to 19.11 > LTS. >=20 Thanks, will do it in next version. > Thanks, > Maxime