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Date: Tue, 27 Jan 2015 11:37:15 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Linhaifeng <haifeng.lin@huawei.com>
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X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23
Cc: "dpd >> dev@dpdk.org" <dev@dpdk.org>, liuyongan@huawei.com
Subject: Re: [dpdk-dev] vhost: virtio-net rx-ring stop work after work many
	hours, bug?
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On Tue, Jan 27, 2015 at 03:57:13PM +0800, Linhaifeng wrote:
> Hi,all
> 
> I use vhost-user to send data to VM at first it cant work well but after many hours VM can not receive data but can send data.
> 
> (gdb)p avail_idx
> $4 = 2668
> (gdb)p free_entries
> $5 = 0
> (gdb)l
>         /* check that we have enough buffers */
>         if (unlikely(count > free_entries))
>             count = free_entries;
> 
>         if (count == 0){
>             int b=0;
>             if(b) { // when set b=1 to notify guest rx_ring will restart to work
>                 if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
> 
>                     eventfd_write(vq->callfd, 1);
>                 }
>             }
>             return 0;
>         }
> 
> some info i print in guest:
> 
> net eth3:vi->num=199
> net eth3:rvq info: num_free=57, used->idx=2668, avail->idx=2668
> net eth3:svq info: num_free=254, used->idx=1644, avail->idx=1644
> 
> net eth3:vi->num=199
> net eth3:rvq info: num_free=57, used->idx=2668, avail->idx=2668
> net eth3:svq info: num_free=254, used->idx=1645, avail->idx=1645
> 
> net eth3:vi->num=199
> net eth3:rvq info: num_free=57, used->idx=2668, avail->idx=2668
> net eth3:svq info: num_free=254, used->idx=1646, avail->idx=1646
> 
> # free
>              total       used       free     shared    buffers     cached
> Mem:      3924100      337252    3586848          0      95984     138060
> -/+ buffers/cache:     103208    3820892
> Swap:       970748          0     970748
> 
> I have two questions:
> 1.Should we need to notify guest when there is no buffer in vq->avail?

No unless NOTIFY_ON_EMPTY is set (most guests don't set it).

> 2.Why virtio_net stop to fill avail?

Most likely, it didn't get an interrupt.

If so, it would be a dpdk vhost user bug.
Which code are you using in dpdk?

> 
> 
> 
> 
> 
> -- 
> Regards,
> Haifeng