From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:58900 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751646AbdIOGWn (ORCPT ); Fri, 15 Sep 2017 02:22:43 -0400 Subject: Patch "vhost_net: correctly check tx avail during rx busy polling" has been added to the 4.9-stable tree To: jasowang@redhat.com, davem@davemloft.net, gregkh@linuxfoundation.org Cc: , From: Date: Thu, 14 Sep 2017 23:22:23 -0700 Message-ID: <150545654311222@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled vhost_net: correctly check tx avail during rx busy polling to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: vhost_net-correctly-check-tx-avail-during-rx-busy-polling.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Thu Sep 14 23:20:08 PDT 2017 From: Jason Wang Date: Tue, 5 Sep 2017 09:22:05 +0800 Subject: vhost_net: correctly check tx avail during rx busy polling From: Jason Wang [ 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 Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- 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); Patches currently in stable-queue which might be from jasowang@redhat.com are queue-4.9/vhost_net-correctly-check-tx-avail-during-rx-busy-polling.patch