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 5778A1B9A5 for ; Thu, 20 Dec 2018 15:30:38 +0100 (CET) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C87A1ED258; Thu, 20 Dec 2018 14:30:37 +0000 (UTC) Received: from redhat.com (ovpn-122-182.rdu2.redhat.com [10.10.122.182]) by smtp.corp.redhat.com (Postfix) with SMTP id 89265605CF; Thu, 20 Dec 2018 14:30:33 +0000 (UTC) Date: Thu, 20 Dec 2018 09:30:30 -0500 From: "Michael S. Tsirkin" To: Maxime Coquelin Cc: dev@dpdk.org, i.maximets@samsung.com, tiwei.bie@intel.com, zhihong.wang@intel.com, jfreiman@redhat.com Message-ID: <20181220092201-mutt-send-email-mst@kernel.org> References: <20181220100022.3531-1-maxime.coquelin@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181220100022.3531-1-maxime.coquelin@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 20 Dec 2018 14:30:37 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH v3] vhost: batch used descs 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: Thu, 20 Dec 2018 14:30:39 -0000 On Thu, Dec 20, 2018 at 11:00:22AM +0100, Maxime Coquelin wrote: > 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 | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > > diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c > index 8c657a101..66ccd3c35 100644 > --- a/lib/librte_vhost/virtio_net.c > +++ b/lib/librte_vhost/virtio_net.c > @@ -97,6 +97,8 @@ flush_shadow_used_ring_packed(struct virtio_net *dev, > { > int i; > uint16_t used_idx = vq->last_used_idx; > + uint16_t head_idx = vq->last_used_idx; > + uint16_t head_flags = 0; > > /* Split loop in two to save memory barriers */ > for (i = 0; i < vq->shadow_used_idx; i++) { > @@ -126,12 +128,17 @@ flush_shadow_used_ring_packed(struct virtio_net *dev, > flags &= ~VRING_DESC_F_AVAIL; > } > > - vq->desc_packed[vq->last_used_idx].flags = flags; > + 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) { > @@ -140,7 +147,15 @@ flush_shadow_used_ring_packed(struct virtio_net *dev, > } > } > > + vq->desc_packed[head_idx].flags = head_flags; > + > rte_smp_wmb(); > + > + vhost_log_cache_used_vring(dev, vq, > + head_idx * > + sizeof(struct vring_packed_desc), > + sizeof(struct vring_packed_desc)); > + > vq->shadow_used_idx = 0; > vhost_log_cache_sync(dev, vq); How about moving rte_smp_wmb into logging functions? This way it's free with log disabled even on arm... > } > -- > 2.17.2