Subject: Re: [iproute PATCH 0/2] Netns performance improvements

From: Rick Jones <[email-masked]>
Date: Thu, 7 Jul 2016 09:16:20 -0700

On 07/07/2016 08:48 AM, Phil Sutter wrote:
> On Thu, Jul 07, 2016 at 02:59:48PM +0200, Nicolas Dichtel wrote:
>> Le 07/07/2016 13:17, Phil Sutter a écrit :
>> [snip]
>>> The issue came up during OpenStack Neutron testing, see this ticket for
>>> reference:
>>>
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1310795
>> Access to this ticket is not public :(
>
> *Sigh* OK, here are a few quotes:
>
> "OpenStack Neutron controller nodes, when undergoing testing, are
> locking up specifically during creation and mounting of namespaces.
> They appear to be blocking behind vfsmount_lock, and contention for the
> namespace_sem"
>
> "During the scale testing, we have 300 routers, 600 dhcp namespaces
> spread across four neutron network nodes. When then start as one set of
> standard Openstack Rally benchmark test cycle against neutron. An
> example scenario is creating 10x networks, list them, delete them and
> repeat 10x times. The second set performs an L3 benchmark test between
> two instances."
>

Those 300 routers will each have at least one namespace along with the 
dhcp namespaces.  Depending on the nature of the routers (Distributed 
versus Centralized Virtual Routers - DVR vs CVR) and whether the routers 
are supposed to be "HA" there can be more than one namespace for a given 
router.

300 routers is far from the upper limit/goal.  Back in HP Public Cloud, 
we were running as many as 700 routers per network node (*), and more 
than four network nodes. (back then it was just the one namespace per 
router and network). Mileage will of course vary based on the "oomph" of 
one's network node(s).

happy benchmarking,

rick jones

* Didn't want to go much higher than that because each router had a port 
on a common linux bridge and getting to > 1024 would be an unpleasant day.