[ovs-discuss] OVN scalability?

Han Zhou zhouhan at gmail.com
Tue Apr 24 00:05:57 UTC 2018


On Mon, Apr 23, 2018 at 12:21 AM, Wei Li <liwei at anbutu.com> wrote:
>
> Hi Han,
>
>
> On 04/19/2018 06:07 AM, Han Zhou wrote:
> > On Wed, Apr 18, 2018 at 1:41 PM, Mike Spreitzer <mspreitz at us.ibm.com>
wrote:
> >> How big a system can OVN manage?  I am told some local experimenters
did
> >> some tests about two years ago, and ran into CPU saturation at the
south
> >> DB at around a hundred hypervisors.
> >>
> >> Thanks,
> >> Mike
> >>
> > In our testing env (setup with
https://github.com/openvswitch/ovn-scale-test),
> > with 1k hypervisors the central node CPU (including NB DB, SB DB and
> > ovn-northd) is still low.
> We observed a high cpu utilization in our environment(about 15 HVs) when
doing
> a high rate of port insertion/deletion. It seems ovn-northd recompute
everything on
> NB change, do you have any optimization suggestion on this scenario?
>
What's the rate of port insertion/deletion in your testing? Since northd
processed NB DB data only, the number of HVs actually doesn't matter. In
our testing the rate was around 1 port/sec, so it was not that hot.
It might trigger hot CPU on northd if NB DB changes very frequently, but it
doesn't mean there is real problem. northd doesn't react to each change,
but instead it computes against the latest data in NB DB. So what matters
is the size of total data in NB DB, and how long it takes for northd to
finish a round of computing for this size of data.

> > CPU is rather busy on HVs, but there is an ongoing optimization with
very
> > promising test result:
> > https://mail.openvswitch.org/pipermail/ovs-dev/2018-April/346136.html
> Is there will be a similar incremental processing for ovn-northd in your
roadmap?
>
Incremental processing for northd has been discussed in this community and
I think it is in the roadmap :) According to previous discussions, the
approach for northd incremental processing will be different from what I am
doing in ovn-controller though. Unlike ovn-controller, the input of northd
is purely NB DB, so the proposal was to rewrite northd with some domain
specific language (a datalog approach) so that the incremental processing
happens in a more clean way. But I am not sure about the progress of this
work. Ben may have more information.

> Thanks,
> Wei
>
> >
> > Thanks,
> > Han
> >
> >
> >
> > _______________________________________________
> > discuss mailing list
> > discuss at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
>
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