* [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* Re: [dpdk-dev] [PATCH] vhost: use SMP memory barrier before kicking guest
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
1 sibling, 0 replies; 3+ messages in thread
From: Tiwei Bie @ 2018-06-12 6:41 UTC (permalink / raw)
To: Maxime Coquelin; +Cc: zhihong.wang, dev
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>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [dpdk-dev] [PATCH] vhost: use SMP memory barrier before kicking guest
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
1 sibling, 0 replies; 3+ messages in thread
From: Maxime Coquelin @ 2018-06-15 8:49 UTC (permalink / raw)
To: zhihong.wang, tiwei.bie, 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 <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
^ 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)
-- links below jump to the message on this page --
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
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).