Net-list is very slow under metaplugin

[Itsuro Oda]

If there are many networks when using metaplugin, net-list (GET networks API)
takes very long time.
For example: (showing hardware spec etc. is omitted since it is relative comparison.)

--- 200 networks, openvswitch plugin used natively
$ time neutron net-list
...snip
real 0m2.007s
user 0m0.428s
sys 0m0.100s
---

--- 200 openvswitch networks, under metaplugin
$ time neutron net-list
...snip
real 0m7.700s
user 0m0.472s
sys 0m0.072s
---
Note that the quantum-server wastes a lot of cpu usage too.

[Itsuro Oda (oda-g)]

Investigation:
The reason of this problem is that the metaplgin calls plugin.get_network()
for each network in the metaplugin's get_networks().
(i.e. if there are 200 networks, get_network() is called 200 times.)

Proposed fix:
Change to call target plugin's get_networks for each taget plugin.
I think it is available to use hook routines.

[yong sheng gong (gongysh)]

It is interesting to know whether there are still people using this plugin when we have ml2.

[Itsuro Oda (oda-g)]

There is still people using metaplugin and note that a third party testing for metaplugin is going to prepare.
(see. https://wiki.openstack.org/wiki/Neutron_Plugins_and_Drivers )

Typical use case of metaplugin is that an OSS plugin (ex. linuxbridge or ml2(with linuxbridge mechanism driver)) and a commercial plugin which does not apply ml2 mechanism (ex. NVP ) are used at the same time.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/70060

[Itsuro Oda (oda-g)]

Note: performance after the fix;
--- 200 openvswitch networks, under metaplugin
$ time neutron net-list
...snip
real 0m2.232s
user 0m0.416s
sys 0m0.124s
---

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/70060
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=a1e1b0a6251c9b0838f871591316c41f37b4b3e0
Submitter: Jenkins
Branch: master

commit a1e1b0a6251c9b0838f871591316c41f37b4b3e0
Author: Itsuro Oda <email address hidden>
Date: Tue Dec 24 12:27:53 2013 +0900

    Enhance GET networks performance of metaplugin

    Change to call plugin.get_networks() per target plugin
    instead of calling plugin.get_network() per network.
    Hook routines are used to select networks which belong
    the target plugin.

    Change-Id: Ieff06ac7bc7a150501f91aecc3197b0bb664d5fa
    Closes-Bug: #1267290