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 60B701B1F2 for ; Wed, 5 Dec 2018 10:50:38 +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 C3BD730944E4; Wed, 5 Dec 2018 09:50:37 +0000 (UTC) Received: from localhost.localdomain (ovpn-112-38.ams2.redhat.com [10.36.112.38]) by smtp.corp.redhat.com (Postfix) with ESMTP id CA7485D757; Wed, 5 Dec 2018 09:50:35 +0000 (UTC) From: Maxime Coquelin To: dev@dpdk.org, jfreimann@redhat.com, tiwei.bie@intel.com, zhihong.wang@intel.com, jasowang@redhat.com Cc: Maxime Coquelin Date: Wed, 5 Dec 2018 10:49:55 +0100 Message-Id: <20181205094957.1938-4-maxime.coquelin@redhat.com> In-Reply-To: <20181205094957.1938-1-maxime.coquelin@redhat.com> References: <20181205094957.1938-1-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 [10.5.110.40]); Wed, 05 Dec 2018 09:50:37 +0000 (UTC) Subject: [dpdk-dev] [PATCH 3/5] vhost: prefetch descriptor after the read barrier 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, 05 Dec 2018 09:50:38 -0000 This patch moves the prefetch after the available index is read to avoid prefetching a descriptor not available yet. Signed-off-by: Maxime Coquelin --- lib/librte_vhost/virtio_net.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c index 68b72e7a5..0a860ca72 100644 --- a/lib/librte_vhost/virtio_net.c +++ b/lib/librte_vhost/virtio_net.c @@ -794,7 +794,6 @@ virtio_dev_rx_split(struct virtio_net *dev, struct vhost_virtqueue *vq, struct buf_vector buf_vec[BUF_VECTOR_MAX]; uint16_t avail_head; - rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]); avail_head = *((volatile uint16_t *)&vq->avail->idx); /* @@ -803,6 +802,8 @@ virtio_dev_rx_split(struct virtio_net *dev, struct vhost_virtqueue *vq, */ rte_smp_rmb(); + rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]); + for (pkt_idx = 0; pkt_idx < count; pkt_idx++) { uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen; uint16_t nr_vec = 0; @@ -1378,8 +1379,6 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq, } } - rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]); - free_entries = *((volatile uint16_t *)&vq->avail->idx) - vq->last_avail_idx; if (free_entries == 0) @@ -1391,6 +1390,8 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq, */ rte_smp_rmb(); + rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]); + VHOST_LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__); count = RTE_MIN(count, MAX_PKT_BURST); -- 2.17.2