lkml.org 
[lkml]   [2017]   [Sep]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.12 39/52] vhost_net: correctly check tx avail during rx busy polling
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasowang@redhat.com>


[ Upstream commit 8b949bef9172ca69d918e93509a4ecb03d0355e0 ]

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/vhost/net.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -557,8 +557,13 @@ static int vhost_net_rx_peek_head_len(st

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(sk);

\
 
 \ /
  Last update: 2017-09-18 11:41    [W:0.380 / U:0.716 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site