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 21CF6A2EFC for ; Mon, 14 Oct 2019 09:42:58 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 939C91C1B9; Mon, 14 Oct 2019 09:42:57 +0200 (CEST) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id D5EB11C1B4 for ; Mon, 14 Oct 2019 09:42:55 +0200 (CEST) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 19036801670; Mon, 14 Oct 2019 07:42:55 +0000 (UTC) Received: from [10.36.112.44] (ovpn-112-44.ams2.redhat.com [10.36.112.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 035E85C28C; Mon, 14 Oct 2019 07:42:45 +0000 (UTC) To: Joyce Kong , dev@dpdk.org Cc: nd@arm.com, yinan.wang@intel.com, bruce.richardson@intel.com, tiwei.bie@intel.com, zhihong.wang@intel.com, amorenoz@redhat.com, xiao.w.wang@intel.com, yong.liu@intel.com, jfreimann@redhat.com, honnappa.nagarahalli@arm.com, gavin.hu@arm.com References: <1568698107-36668-1-git-send-email-joyce.kong@arm.com> <1568698107-36668-2-git-send-email-joyce.kong@arm.com> From: Maxime Coquelin Autocrypt: addr=maxime.coquelin@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <1568698107-36668-2-git-send-email-joyce.kong@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.67]); Mon, 14 Oct 2019 07:42:55 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH v4 1/2] virtio: one way barrier for packed vring desc avail flags 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" On 9/17/19 7:28 AM, Joyce Kong wrote: > In case VIRTIO_F_ORDER_PLATFORM(36) is not negotiated, then the frontend > and backend are assumed to be implemented in software, that is they can > run on identical CPUs in an SMP configuration. > Thus a weak form of memory barriers like rte_smp_r/wmb, other than > rte_cio_r/wmb, is sufficient for this case(vq->hw->weak_barriers == 1) > and yields better performance. > For the above case, this patch helps yielding even better performance > by replacing the two-way barriers with C11 one-way barriers for avail > flags in packed ring. > > Meanwhile, a read barrier is required to ensure ordering between > descriptor's flags and content reads[1]. With C11, load-acquire can > enforce the ordering instead of rmb barrier. > > [1]https://patchwork.dpdk.org/patch/49109/ > > Signed-off-by: Joyce Kong > Reviewed-by: Gavin Hu > Reviewed-by: Phil Yang > Reviewed-by: Maxime Coquelin > --- > drivers/net/virtio/virtio_rxtx.c | 13 +++++++------ > drivers/net/virtio/virtio_user/virtio_user_dev.c | 6 +++++- > drivers/net/virtio/virtqueue.h | 21 +++++++++++++++++++++ > lib/librte_vhost/vhost.h | 2 +- > lib/librte_vhost/virtio_net.c | 11 +++++------ > 5 files changed, 39 insertions(+), 14 deletions(-) > Reviewed-by: Maxime Coquelin Thanks, Maxime