Re: XSA-332 kernel patch - huge network performance on pfSense VMs

[Samuel Verschelde <samuel.verschelde@vates.fr>]

Le 18/01/2021 à 11:03, Roger Pau Monné a écrit :
> On Fri, Jan 15, 2021 at 03:03:26PM +0000, Samuel Verschelde wrote:
>> Hi list,
>>
>> Another "popular" thread on XCP-ng forum [1], started in october 2020,
>> allowed us to detect that patch 12 from the XSA-332 advisory [2] had a very
>> significant impact on network performance in the case of pfSense VMs.
>>
>> We reproduced the issue internally (well, we reproduced "something". The
>> user setups in this thread are diverse) and our findings seem to confirm
>> what the users reported. Running iperf3 from the pfSense VM to a debian VM
>> gives results around 5 times slower than before. Reverting this single patch
>> brings the performance back. On the debian to pfSense direction, the drop is
>> about 25%.
>
> pfSense is based on FreeBSD, so I would bet that whatever performance
> degradation you are seeing would also happen with plain FreeBSD. I
> would assume netfront in FreeBSD is triggering the ratelimit on Linux,
> and hence it gets throttled.
>
> Do you think you have the bandwidth to look into the FreeBSD side and
> try to provide a fix? I'm happy to review and commit in upstream
> FreeBSD, but would be nice to have someone else also in the loop as
> ATM I'm the only one doing FreeBSD/Xen development AFAIK.
>
> Thanks, Roger.
>

(sorry about the previous email, looks like my mail client hates me)

I would personnally not be able to hack into either Xen, the linux
kernel or FreeBSD in any efficient way. My role here is limited to
packaging, testing and acting as a relay between users and developers.
We currently don't have anyone at Vates who would be able to hack into
FreeBSD either.

What currently put FreeBSD on our radar is the large amount of users who
use FreeNAS/TrueNAS or pfSense VMs, and the recent bugs they detected
(XSA-360 and this performance drop).

Additionnally, regarding this performance issue, some users report an
impact of that same patch 12 on the network performance of their non-BSD
VMs [1][2], so I think the FreeBSD case might be helpful to help
identify what in that patch caused throttling (if that's what happens),
because it's easier to reproduce, but I'm not sure fixes would only need
to be made in FreeBSD.

Best regards,

Samuel Verschelde

[1] https://xcp-ng.org/forum/post/35521 mentions debian based Untangle
OS and inter-VLAN traffic
[2] https://xcp-ng.org/forum/post/35476 general slowdown affecting all
VMs (VM to workstation traffic), from the first user who identified
patch 12 as the cause.