From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH] vhost: use SMP memory barrier before kicking guest Date: Fri, 15 Jun 2018 10:49:04 +0200 Message-ID: <9c48d964-cc32-2ac6-e12d-e66973b09bfd@redhat.com> References: <20180607143826.23647-1-maxime.coquelin@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit To: zhihong.wang@intel.com, tiwei.bie@intel.com, dev@dpdk.org Return-path: Received: from mx1.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by dpdk.org (Postfix) with ESMTP id B82991D8CC for ; Fri, 15 Jun 2018 10:49:07 +0200 (CEST) In-Reply-To: <20180607143826.23647-1-maxime.coquelin@redhat.com> Content-Language: en-US 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 06/07/2018 04:38 PM, Maxime Coquelin wrote: > vhost_vring_call() used rte_mb(), which translates into > mfence instruction on x86. > > This patch changes to use rte_smp_mb(), which changed recently > to translate into a locked ADD instruction for performance > reason. > > The measured gain is up to 3% with the testpmd benchmarks. > > Signed-off-by: Maxime Coquelin > --- > lib/librte_vhost/vhost.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h > index 58c425a5c..1bc99ed3c 100644 > --- a/lib/librte_vhost/vhost.h > +++ b/lib/librte_vhost/vhost.h > @@ -591,7 +591,7 @@ static __rte_always_inline void > vhost_vring_call(struct virtio_net *dev, struct vhost_virtqueue *vq) > { > /* Flush used->idx update before we read avail->flags. */ > - rte_mb(); > + rte_smp_mb(); > > /* Don't kick guest if we don't reach index specified by guest. */ > if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) { > Applied to dpdk-next-virtio Thanks, Maxime