From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH] vhost-net: add time limitation for tx polling Date: Tue, 27 Mar 2018 17:40:28 +0800 Message-ID: <182a4eaf-205d-b2b7-6f10-a23ec597f840@redhat.com> References: <88D661ADF6AFBF42B2AB88D8E7682B0901FC4059@EXMBX-SZMAIL011.tencent.com> Mime-Version: 1.0 Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit To: =?UTF-8?B?aGFpYmluemhhbmco5byg5rW35paMKQ==?= , "mst@redhat.com" , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Return-path: In-Reply-To: <88D661ADF6AFBF42B2AB88D8E7682B0901FC4059@EXMBX-SZMAIL011.tencent.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 2018年03月27日 17:12, haibinzhang(张海斌) wrote: > handle_tx() will delay rx for a long time when busy tx polling udp packets > with short length(ie: 1byte udp payload), because setting VHOST_NET_WEIGHT > takes into account only sent-bytes but no time. Interesting. Looking at vhost_can_busy_poll() it tries to poke pending vhost work and exit the busy loop if it found one. So I believe something block the work queuing. E.g did reverting 8241a1e466cd56e6c10472cac9c1ad4e54bc65db fix the issue? > It's not fair for handle_rx(), > so needs to limit max time of tx polling. > > Signed-off-by: Haibin Zhang > --- > drivers/vhost/net.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 8139bc70ad7d..dc9218a3a75b 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -473,6 +473,7 @@ static void handle_tx(struct vhost_net *net) > struct socket *sock; > struct vhost_net_ubuf_ref *uninitialized_var(ubufs); > bool zcopy, zcopy_used; > + unsigned long start = jiffies; Checking jiffies is tricky, need to convert it to ms or whatever others. > > mutex_lock(&vq->mutex); > sock = vq->private_data; > @@ -580,7 +581,7 @@ static void handle_tx(struct vhost_net *net) > else > vhost_zerocopy_signal_used(net, vq); > vhost_net_tx_packet(net); > - if (unlikely(total_len >= VHOST_NET_WEIGHT)) { > + if (unlikely(total_len >= VHOST_NET_WEIGHT) || unlikely(jiffies - start >= 1)) { How value 1 is determined here? And we need a complete test to make sure this won't affect other use cases. Another thought is introduce another limit of #packets, but this need benchmark too. Thanks > vhost_poll_queue(&vq->poll); > break; > }