Messages in this thread | | | Subject | Re: [PATCH] vhost-net: add time limitation for tx polling | From | Jason Wang <> | Date | Tue, 27 Mar 2018 17:40:28 +0800 |
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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 <haibinzhang@tencent.com> > --- > 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; > }
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