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 1839C1B205 for ; Wed, 28 Nov 2018 10:47:12 +0100 (CET) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5DA8B76528; Wed, 28 Nov 2018 09:47:11 +0000 (UTC) Received: from localhost.localdomain (ovpn-112-54.ams2.redhat.com [10.36.112.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id 17848101962B; Wed, 28 Nov 2018 09:47:02 +0000 (UTC) From: Maxime Coquelin To: dev@dpdk.org, tiwei.bie@intel.com, zhihong.wang@intel.com, jfreimann@redhat.com Cc: Maxime Coquelin Date: Wed, 28 Nov 2018 10:47:00 +0100 Message-Id: <20181128094700.14598-1-maxime.coquelin@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Wed, 28 Nov 2018 09:47:11 +0000 (UTC) Subject: [dpdk-dev] [PATCH] vhost: batch used descriptors chains write-back with packed ring 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, 28 Nov 2018 09:47:12 -0000 Instead of writing back descriptors chains in order, let's write the first chain flags last in order to improve batching. With Kernel's pktgen benchmark, ~3% performance gain is measured. Signed-off-by: Maxime Coquelin --- lib/librte_vhost/virtio_net.c | 37 ++++++++++++++++++++++------------- 1 file changed, 23 insertions(+), 14 deletions(-) diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c index 5e1a1a727..f54642c2d 100644 --- a/lib/librte_vhost/virtio_net.c +++ b/lib/librte_vhost/virtio_net.c @@ -135,19 +135,10 @@ flush_shadow_used_ring_packed(struct virtio_net *dev, struct vhost_virtqueue *vq) { int i; - uint16_t used_idx = vq->last_used_idx; + uint16_t head_flags, head_idx = vq->last_used_idx; - /* Split loop in two to save memory barriers */ - for (i = 0; i < vq->shadow_used_idx; i++) { - vq->desc_packed[used_idx].id = vq->shadow_used_packed[i].id; - vq->desc_packed[used_idx].len = vq->shadow_used_packed[i].len; - - used_idx += vq->shadow_used_packed[i].count; - if (used_idx >= vq->size) - used_idx -= vq->size; - } - - rte_smp_wmb(); + if (unlikely(vq->shadow_used_idx == 0)) + return; for (i = 0; i < vq->shadow_used_idx; i++) { uint16_t flags; @@ -165,12 +156,22 @@ flush_shadow_used_ring_packed(struct virtio_net *dev, flags &= ~VRING_DESC_F_AVAIL; } - vq->desc_packed[vq->last_used_idx].flags = flags; + vq->desc_packed[vq->last_used_idx].id = + vq->shadow_used_packed[i].id; + vq->desc_packed[vq->last_used_idx].len = + vq->shadow_used_packed[i].len; + + if (i > 0) { + vq->desc_packed[vq->last_used_idx].flags = flags; - vhost_log_cache_used_vring(dev, vq, + vhost_log_cache_used_vring(dev, vq, vq->last_used_idx * sizeof(struct vring_packed_desc), sizeof(struct vring_packed_desc)); + } else { + head_idx = vq->last_used_idx; + head_flags = flags; + } vq->last_used_idx += vq->shadow_used_packed[i].count; if (vq->last_used_idx >= vq->size) { @@ -180,7 +181,15 @@ flush_shadow_used_ring_packed(struct virtio_net *dev, } rte_smp_wmb(); + + vq->desc_packed[head_idx].flags = head_flags; vq->shadow_used_idx = 0; + + vhost_log_cache_used_vring(dev, vq, + head_idx * + sizeof(struct vring_packed_desc), + sizeof(struct vring_packed_desc)); + vhost_log_cache_sync(dev, vq); } -- 2.17.2