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* [dpdk-dev] [PATCH] vhost: use SMP memory barrier before kicking guest
@ 2018-06-07 14:38 Maxime Coquelin
  2018-06-12  6:41 ` Tiwei Bie
  2018-06-15  8:49 ` Maxime Coquelin
  0 siblings, 2 replies; 3+ messages in thread
From: Maxime Coquelin @ 2018-06-07 14:38 UTC (permalink / raw)
  To: zhihong.wang, tiwei.bie, dev; +Cc: Maxime Coquelin

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

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2018-06-15  8:49 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2018-06-07 14:38 [dpdk-dev] [PATCH] vhost: use SMP memory barrier before kicking guest Maxime Coquelin
2018-06-12  6:41 ` Tiwei Bie
2018-06-15  8:49 ` Maxime Coquelin

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