Re: [PATCH net V2] vhost_net: correctly check tx avail during rx busy polling

[David Miller]

From: Jason Wang <jasowang@xxxxxxxxxx>
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@xxxxxxxxxx>

Applied and queued up for -stable, thanks.