lkml.org 
[lkml]   [2017]   [Sep]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH net] vhost_net: correctly check tx avail during rx busy polling
Date
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
---
drivers/vhost/net.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 06d0448..1b68253 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -634,7 +634,7 @@ 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);
mutex_unlock(&vq->mutex);

--
2.7.4
\
 
 \ /
  Last update: 2017-09-01 11:03    [W:0.054 / U:2.464 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site