Open Stack

On Fri, Dec 27, 2013 at 11:09:02AM +0100,
Salvatore Orlando <sorlando at nicira.com> wrote:

> Hi,
> 
> We now have several patches under review which improve a lot how neutron
> handles parallel testing.
> In a nutshell, these patches try to ensure the ovs agent processes new,
> removed, and updated interfaces as soon as possible,
> 
> These patches are:
> https://review.openstack.org/#/c/61105/
> https://review.openstack.org/#/c/61964/
> https://review.openstack.org/#/c/63100/
> https://review.openstack.org/#/c/63558/
> 
> There is still room for improvement. For instance the calls from the agent
> into the plugins might be consistently reduced.
> However, even if the above patches shrink a lot the time required for
> processing a device, we are still hitting a hard limit with the execution
> ovs commands for setting local vlan tags and clearing flows (or adding the
> flow rule for dropping all the traffic).
> In some instances this commands slow down a lot, requiring almost 10
> seconds to complete. This adds a delay in interface processing which in
> some cases leads to the hideous SSH timeout error (the same we see with bug
> 1253896 in normal testing).
> It is also worth noting that when this happens sysstat reveal CPU usage is
> very close to 100%
> 
> From the neutron side there is little we can do. Introducing parallel
> processing for interface, as we do for the l3 agent, is not actually a
> solution, since ovs-vswitchd v1.4.x, the one executed on gate tests, is not
> multithreaded. If you think the situation might be improved by changing the
> logic for handling local vlan tags and putting ports on the dead vlan, I
> would be happy to talk about that.

How about batching those ovsdb operations?
Instead of issueing many ovs-vsctl command,
ovs-vsctl -- command0 [args] -- command1 [args] -- ...

Then, the number of ovs-vsctl will be reduced and ovs-vsctl issues
only single ovsdb transaction.
-- 
Isaku Yamahata <isaku.yamahata at gmail.com>