[dpdk-users] Drops seems with virtio PMD driver

[dpdk-users] Drops seems with virtio PMD driver

[Venumadhav Josyula]

Hi All,

We are observing packet drops ~@90Mbs with virtio pmd driver. These packets
are not been
queued in the tx descriptors, the function 'rte_eth_tx_burst' is returning
the less than n.

So questions are following
i)  are there any issues seen ?

Observations in our case :-
i) packets are dropped and tx packets donot get incremented.
ii) i) happens for 30 secs after that it recovers.
iii) After sometime we see this issue in i) & ii) again.

Any clues / pointers will help.

Thanks,
Regards,
Venu

Re: [dpdk-users] Drops seems with virtio PMD driver

[Stephen Hemminger]

On Thu, 29 Aug 2019 10:12:27 +0530
Venumadhav Josyula <vjosyula@gmail.com> wrote:

> Hi All,
> 
> We are observing packet drops ~@90Mbs with virtio pmd driver. These packets
> are not been
> queued in the tx descriptors, the function 'rte_eth_tx_burst' is returning
> the less than n.
> 
> So questions are following
> i)  are there any issues seen ?
> 
> Observations in our case :-
> i) packets are dropped and tx packets donot get incremented.
> ii) i) happens for 30 secs after that it recovers.
> iii) After sometime we see this issue in i) & ii) again.
> 
> Any clues / pointers will help.
> 
> Thanks,
> Regards,
> Venu

The number of transmit descriptors is fixed.
If you are producing packets faster than the other consume them then the
transmit descriptor ring gets full. So the problem is probably on the other
side of your virtio. Are you using KVM? Did you enable virtio net acceleration?

Re: [dpdk-users] Drops seems with virtio PMD driver

[Venumadhav Josyula]

Hi Stephen,
 >Are you using KVM?
Yes
>Did you enable virtio net acceleration?
Will get back to you. Can you let me what are benefits of it ?

Thanks,
Regards
Venu

On Thu, 29 Aug 2019 at 20:10, Stephen Hemminger <stephen@networkplumber.org>
wrote:

> On Thu, 29 Aug 2019 10:12:27 +0530
> Venumadhav Josyula <vjosyula@gmail.com> wrote:
>
> > Hi All,
> >
> > We are observing packet drops ~@90Mbs with virtio pmd driver. These
> packets
> > are not been
> > queued in the tx descriptors, the function 'rte_eth_tx_burst' is
> returning
> > the less than n.
> >
> > So questions are following
> > i)  are there any issues seen ?
> >
> > Observations in our case :-
> > i) packets are dropped and tx packets donot get incremented.
> > ii) i) happens for 30 secs after that it recovers.
> > iii) After sometime we see this issue in i) & ii) again.
> >
> > Any clues / pointers will help.
> >
> > Thanks,
> > Regards,
> > Venu
>
> The number of transmit descriptors is fixed.
> If you are producing packets faster than the other consume them then the
> transmit descriptor ring gets full. So the problem is probably on the other
> side of your virtio. Are you using KVM? Did you enable virtio net
> acceleration?
>

Re: [dpdk-users] Drops seems with virtio PMD driver

[Stephen Hemminger]

On Thu, 29 Aug 2019 20:12:54 +0530
Venumadhav Josyula <vjosyula@gmail.com> wrote:

> Hi Stephen,
>  >Are you using KVM?  
> Yes
> >Did you enable virtio net acceleration?  
> Will get back to you. Can you let me what are benefits of it ?
> 
> Thanks,
> Regards
> Venu

Without virtio net acceleration packets take longer path through QEMU
in userspace.  Acceleration keeps packets in kernel.