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| Started by | Jason Wang <jasowang@redhat.com> |
|---|---|
| First post | 2017-09-05 03:30 +0200 |
| Last post | 2017-09-05 23:50 +0200 |
| Articles | 2 — 2 participants |
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[PATCH net V2] vhost_net: correctly check tx avail during rx busy polling Jason Wang <jasowang@redhat.com> - 2017-09-05 03:30 +0200
Re: [PATCH net V2] vhost_net: correctly check tx avail during rx busy polling David Miller <davem@davemloft.net> - 2017-09-05 23:50 +0200
| From | Jason Wang <jasowang@redhat.com> |
|---|---|
| Date | 2017-09-05 03:30 +0200 |
| Subject | [PATCH net V2] vhost_net: correctly check tx avail during rx busy polling |
| Message-ID | <umaQF-4ws-1@gated-at.bofh.it> |
We check tx avail through vhost_enable_notify() in the past which is
wrong since it only checks whether or not guest has filled more
available buffer since last avail idx synchronization which was just
done by vhost_vq_avail_empty() before. What we really want is checking
pending buffers in the avail ring. Fix this by calling
vhost_vq_avail_empty() instead.
This issue could be noticed by doing netperf TCP_RR benchmark as
client from guest (but not host). With this fix, TCP_RR from guest to
localhost restores from 1375.91 trans per sec to 55235.28 trans per
sec on my laptop (Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz).
Fixes: 030881372460 ("vhost_net: basic polling support")
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
- The patch is needed for -stable
- Changes from V1: enable vq notification when needed
---
drivers/vhost/net.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 06d0448..1c75572 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -634,8 +634,13 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
preempt_enable();
- if (vhost_enable_notify(&net->dev, vq))
+ if (!vhost_vq_avail_empty(&net->dev, vq))
vhost_poll_queue(&vq->poll);
+ else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+ vhost_disable_notify(&net->dev, vq);
+ vhost_poll_queue(&vq->poll);
+ }
+
mutex_unlock(&vq->mutex);
len = peek_head_len(rvq, sk);
--
2.7.4
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| From | David Miller <davem@davemloft.net> |
|---|---|
| Date | 2017-09-05 23:50 +0200 |
| Subject | Re: [PATCH net V2] vhost_net: correctly check tx avail during rx busy polling |
| Message-ID | <umtTk-8sT-11@gated-at.bofh.it> |
| In reply to | #1726302 |
From: Jason Wang <jasowang@redhat.com>
Date: Tue, 5 Sep 2017 09:22:05 +0800
> We check tx avail through vhost_enable_notify() in the past which is
> wrong since it only checks whether or not guest has filled more
> available buffer since last avail idx synchronization which was just
> done by vhost_vq_avail_empty() before. What we really want is checking
> pending buffers in the avail ring. Fix this by calling
> vhost_vq_avail_empty() instead.
>
> This issue could be noticed by doing netperf TCP_RR benchmark as
> client from guest (but not host). With this fix, TCP_RR from guest to
> localhost restores from 1375.91 trans per sec to 55235.28 trans per
> sec on my laptop (Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz).
>
> Fixes: 030881372460 ("vhost_net: basic polling support")
> Signed-off-by: Jason Wang <jasowang@redhat.com>
Applied and queued up for -stable, thanks.
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