[Openstack-stable-maint] Neutron backports for security group performance

Claudiu Belu cbelu at cloudbasesolutions.com
Wed Oct 29 13:24:53 UTC 2014


1. Miguel: Ideally, yes, it should be enough to validate the backports. But most of the CIs will run a subset of the tempest tests that may or may not include tempest.scenario.test_security_groups_basic_ops, which tests the functionality of the security groups on the compute nodes. But this would be a problem on master too.. 

2. Dolph: good point, a benchmark is appropriate in this scenario. It will help us decide whether the backports are worth the risk they have or not. I also agree with the fact that low enough performance is a kind of bug.

3. Thierry: I agree, those backports have a risk of regression, but low performance is a problem too. We should at least see the benchmark results and then decide whether the gain significantly outweighs the risk or not. :)

________________________________________
From: Ihar Hrachyshka [ihrachys at redhat.com]
Sent: Wednesday, October 29, 2014 3:09 PM
To: openstack-stable-maint at lists.openstack.org
Cc: kevinbenton at buttewifi.com
Subject: Re: [Openstack-stable-maint] Neutron backports for security group performance

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On 29/10/14 14:00, Dolph Mathews wrote:
>
> On Wed, Oct 29, 2014 at 5:23 AM, Ihar Hrachyshka
> <ihrachys at redhat.com <mailto:ihrachys at redhat.com>> wrote:
>
> Hi all,
>
> there is a series of Neutron backports in the Juno queue that are
> intended to significantly improve service performance when
> handling security groups (one of the issues that are main pain
> points of current users):
>
> - https://review.openstack.org/130101 -
> https://review.openstack.org/130098 -
> https://review.openstack.org/130100 -
> https://review.openstack.org/130097 -
> https://review.openstack.org/130105
>
> The first four patches are optimizing db side (controller), while
> the last one is to avoid fetching security group rules by OVS agent
> when firewall is disabled.
>
> AFAIK we don't generally backport performance improvements unless
> they are very significant (though I don't see anything written in
> stone that says so), but knowing that those patches fix pain
> hotspots in Neutron, and seem rather isolated, should we consider
> their inclusion?
>
> Should we come up with some "official" rule on how we handle
> performance enhancement backports?
>
>
>> I'm very much in favor of backporting known performance
>> improvements, but in my experience, not all "performance
>> improvements" actually improve performance, so I'd expect an
>> appropriate benchmark to demonstrate a real performance benefit
>> to coincide with the proposed patch.

Exactly. That's what I asked to elaborate on at:
https://review.openstack.org/#/c/130101/

Also, adding Kevin into CC to make sure he is aware of the discussion.

>
>> For a hypothetical example, what seems like a clear cut
>> improvement in review 130098 (remove unused columns from a query)
>> *might* have an unforeseen side effect later on, where another
>> component doesn't have the data it needs, so it suddenly starts
>> issuing a new DB query to compensate. OpenStack is certainly
>> complicated enough that it's impossible to make accurate
>> assumptions about performance.
>
>
>
> /Ihar
>
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