From: Tiwei Bie <tiwei.bie@intel.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: zhihong.wang@intel.com, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] vhost: use SMP memory barrier before kicking guest
Date: Tue, 12 Jun 2018 14:41:58 +0800 [thread overview]
Message-ID: <20180612064157.GB14993@debian> (raw)
In-Reply-To: <20180607143826.23647-1-maxime.coquelin@redhat.com>
On Thu, Jun 07, 2018 at 04:38:26PM +0200, 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)) {
> --
> 2.14.3
>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
next prev parent reply other threads:[~2018-06-12 6:41 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 [this message]
2018-06-15 8:49 ` Maxime Coquelin
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