[openstack-dev] [Neutron] OVS flow modification performance
Miguel Angel Ajo Pelayo
majopela at redhat.com
Mon Apr 11 12:42:59 UTC 2016
On Mon, Apr 11, 2016 at 11:40 AM, IWAMOTO Toshihiro
<iwamoto at valinux.co.jp> wrote:
> At Fri, 8 Apr 2016 12:21:21 +0200,
> Miguel Angel Ajo Pelayo wrote:
>> Hi, good that you're looking at this,
>> You could create a lot of ports with this method  and a bit of extra
>> bash, without the extra expense of instance RAM.
>> This effort is going to be still more relevant in the context of
>> openvswitch firewall. We still need to make sure it's tested with the
>> native interface, and eventually we will need flow bundling (like in
>> ovs-ofctl --bundle add-flows) where the whole addition/removal/modification
>> is sent to be executed atomically by the switch.
> Bad news is that ovs-firewall isn't currently using the native
> of_interface much. I can add install_xxx methods to
> OpenFlowSwitchMixin classes so that ovs-firewall can use the native
> Do you have a plan for implementing flow bundling or using conjunction?
Adding Jakub to the thread,
IMO, if the native interface is going to provide us with greater speed
for rule manipulation, we should look into it.
We don't use bundling or conjunctions yet, but it's part of the plan.
Bundling will allow atomicity of operations with rules (switching
firewall rules, etc, as we have with iptables-save /
iptables-restore), and conjunctions will reduce the number of entries.
(No expansion of IP addresses for remote groups, no expansion of
security group rules per port, when several ports are on the same
security group on the same compute host).
Do we have any metric of bare rule manipulation time (ms/rule, for example)?
As a note, we're around 80 rules/port with IPv6 + IPv4 on the default
sec group plus a couple of rules.
>> On Thu, Apr 7, 2016 at 10:00 AM, IWAMOTO Toshihiro <iwamoto at valinux.co.jp>
>> > At Thu, 07 Apr 2016 16:33:02 +0900,
>> > IWAMOTO Toshihiro wrote:
>> > >
>> > > At Mon, 18 Jan 2016 12:12:28 +0900,
>> > > IWAMOTO Toshihiro wrote:
>> > > >
>> > > > I'm sending out this mail to share the finding and discuss how to
>> > > > improve with those interested in neutron ovs performance.
>> > > >
>> > > > TL;DR: The native of_interface code, which has been merged recently
>> > > > and isn't default, seems to consume less CPU time but gives a mixed
>> > > > result. I'm looking into this for improvement.
>> > >
>> > > I went on to look at implementation details of eventlet etc, but it
>> > > turned out to be fairly simple. The OVS agent in the
>> > > of_interface=native mode waits for a openflow connection from
>> > > ovs-vswitchd, which can take up to 5 seconds.
>> > >
>> > > Please look at the attached graph.
>> > > The x-axis is time from agent restarts, the y-axis is numbers of ports
>> > > processed (in treat_devices and bind_devices). Each port is counted
>> > > twice; the first slope is treat_devices and the second is
>> > > bind_devices. The native of_interface needs some more time on
>> > > start-up, but bind_devices is about 2x faster.
>> > >
>> > > The data was collected with 160 VMs with the devstack default settings.
>> > And if you wonder how other services are doing meanwhile, here is a
>> > bonus chart.
>> > The ovs agent was restarted 3 times with of_interface=native, then 3
>> > times with of_interface=ovs-ofctl.
>> > As the test machine has 16 CPUs, 6.25% CPU usage can mean a single
>> > threaded process is CPU bound.
>> > Frankly, the OVS agent would have little rooms for improvement than
>> > other services. Also, it might be fun to draw similar charts for
>> > other types of workloads.
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