| From foo@baz Thu Sep 14 23:20:08 PDT 2017 |
| From: Jason Wang <jasowang@redhat.com> |
| Date: Tue, 5 Sep 2017 09:22:05 +0800 |
| Subject: vhost_net: correctly check tx avail during rx busy polling |
| |
| 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 |
| @@ -537,8 +537,13 @@ 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); |
