From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 8E4D31B5FB; Wed, 19 Dec 2018 16:49:43 +0100 (CET) Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E4B7EE8B16; Wed, 19 Dec 2018 15:49:42 +0000 (UTC) Received: from redhat.com (ovpn-120-67.rdu2.redhat.com [10.10.120.67]) by smtp.corp.redhat.com (Postfix) with SMTP id CDA8C5D6A9; Wed, 19 Dec 2018 15:49:39 +0000 (UTC) Date: Wed, 19 Dec 2018 10:49:38 -0500 From: "Michael S. Tsirkin" To: Maxime Coquelin Cc: dev@dpdk.org, i.maximets@samsung.com, tiwei.bie@intel.com, zhihong.wang@intel.com, jasowang@redhat.com, stable@dpdk.org Message-ID: <20181219104840-mutt-send-email-mst@kernel.org> References: <20181219082113.24455-1-maxime.coquelin@redhat.com> <20181219082113.24455-5-maxime.coquelin@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181219082113.24455-5-maxime.coquelin@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 19 Dec 2018 15:49:43 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH v2 4/4] vhost: remove useless prefetch for packed ring descriptor 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: , X-List-Received-Date: Wed, 19 Dec 2018 15:49:43 -0000 On Wed, Dec 19, 2018 at 09:21:13AM +0100, Maxime Coquelin wrote: > This prefetch does not show any performance improvement. > > Signed-off-by: Maxime Coquelin Likely because of the RMB. Try prefetching the *next* descriptor maybe? > --- > lib/librte_vhost/virtio_net.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c > index a9be633de..4d201a3fd 100644 > --- a/lib/librte_vhost/virtio_net.c > +++ b/lib/librte_vhost/virtio_net.c > @@ -1437,8 +1437,6 @@ virtio_dev_tx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq, > { > uint16_t i; > > - rte_prefetch0(&vq->desc_packed[vq->last_avail_idx]); > - > if (unlikely(dev->dequeue_zero_copy)) { > struct zcopy_mbuf *zmbuf, *next; > > -- > 2.17.2