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

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Date:	Fri, 8 Jul 2016 10:01:13 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	Rick Jones <rick.jones2@....com>, Phil Sutter <phil@....cc>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Stephen Hemminger <shemming@...cade.com>,
	netdev@...r.kernel.org
Subject: Re: [iproute PATCH 0/2] Netns performance improvements

Le 07/07/2016 18:16, Rick Jones a écrit :
> 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).
Thank you for the details.

Do you have a script or something else to easily reproduce this problem?