From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: zhihong.wang@intel.com, tiwei.bie@intel.com, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] vhost: use SMP memory barrier before kicking guest
Date: Fri, 15 Jun 2018 10:49:04 +0200 [thread overview]
Message-ID: <9c48d964-cc32-2ac6-e12d-e66973b09bfd@redhat.com> (raw)
In-Reply-To: <20180607143826.23647-1-maxime.coquelin@redhat.com>
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 <maxime.coquelin@redhat.com>
> ---
> 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
prev parent reply other threads:[~2018-06-15 8:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-07 14:38 Maxime Coquelin
2018-06-12 6:41 ` Tiwei Bie
2018-06-15 8:49 ` Maxime Coquelin [this message]
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