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 27114A0563; Wed, 15 Apr 2020 16:55:24 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 097871D904; Wed, 15 Apr 2020 16:55:24 +0200 (CEST) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id F1AAB1C1F7 for ; Wed, 15 Apr 2020 16:55:22 +0200 (CEST) IronPort-SDR: s2Fyw32nGxTvSeFnDBZ3IZHBjZOlRWT1lSKytN2S05WwclTri/psLxH71OCwt94wTvMK3MjXIM jiNj9+4R/Kwg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2020 07:55:21 -0700 IronPort-SDR: 8ep26z8+Na1V0kdaj8FWm++ndokL7p1Y1L9Eo9ITMaXMwJh9sphYH9jeuMyroXFyE7/SL1oT+O rpkEi08MnbcA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,387,1580803200"; d="scan'208";a="453951159" Received: from fmsmsx103.amr.corp.intel.com ([10.18.124.201]) by fmsmga005.fm.intel.com with ESMTP; 15 Apr 2020 07:55:21 -0700 Received: from fmsmsx605.amr.corp.intel.com (10.18.126.85) by FMSMSX103.amr.corp.intel.com (10.18.124.201) with Microsoft SMTP Server (TLS) id 14.3.439.0; Wed, 15 Apr 2020 07:55:21 -0700 Received: from fmsmsx605.amr.corp.intel.com (10.18.126.85) by fmsmsx605.amr.corp.intel.com (10.18.126.85) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Wed, 15 Apr 2020 07:55:21 -0700 Received: from shsmsx102.ccr.corp.intel.com (10.239.4.154) by fmsmsx605.amr.corp.intel.com (10.18.126.85) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1713.5 via Frontend Transport; Wed, 15 Apr 2020 07:55:20 -0700 Received: from shsmsx103.ccr.corp.intel.com ([169.254.4.146]) by shsmsx102.ccr.corp.intel.com ([169.254.2.138]) with mapi id 14.03.0439.000; Wed, 15 Apr 2020 22:55:19 +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: AQHWCCz0NVLTzMDwtkaaCNuZzDJ9nqh5yi2AgACMkXA= Date: Wed, 15 Apr 2020 14:55:18 +0000 Message-ID: <86228AFD5BCD8E4EBFD2B90117B5E81E63536963@SHSMSX103.ccr.corp.intel.com> References: <20200401212926.74989-1-yong.liu@intel.com> In-Reply-To: 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 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 >=20 >=20 >=20 > 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. >=20 > 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? >=20 Hi Maxime, The statement is for the different situations between virtio-net + vhost pm= d and virtio-user + vhost pmd in ovs.=20 When combination is virtio-user + vhost pmd in ovs, frontend will be much f= aster than backend. Defer used ring update won't give benefit when requiri= ng zero packet loss.=20 Regards, Marvin > > Solution is just remove deferred shadow update, which will help RFC2544 > > and fix potential issue with virtio net driver. >=20 > What is the potential issue? >=20 > Maxime It is napi stops issue which has been fixed by Eugenio.