| Message ID | 1504574525-4711-1-git-send-email-jasowang@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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.
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);
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(-)