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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: zhihong.wang@intel.com,
tiwei.bie@intel.com,
dev@dpdk.org
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Thu, 7 Jun 2018 16:38:26 +0200
Message-Id: <20180607143826.23647-1-maxime.coquelin@redhat.com>
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Subject: [dpdk-dev] [PATCH] vhost: use SMP memory barrier before kicking
guest
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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