From: Jason Wang Date: Tue, 5 Sep 2017 01:22:05 +0000 (+0800) Subject: vhost_net: correctly check tx avail during rx busy polling X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=8b949bef9172ca69d918e93509a4ecb03d0355e0;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git vhost_net: correctly check tx avail during rx busy polling 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 Signed-off-by: David S. Miller --- diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 8d2bcae53a2e..58585ec8699e 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -635,8 +635,13 @@ 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);