[Bug 1280370] [NEW] high latency between VMs in openstack using OVS

[Chris J Arges]

Public bug reported:

SRU Justification:
[Impact]
* There is high latency when testing latency between VMs in an Openstack environment.
* This affects OVS in P/Q.

[Test Case]
* Setup Openstack.
* On a compute node create at least 15 tenants and add 50 instances (more instances show larger latencies).
* From the Neutron node ping to a particular instance:
ip netns exec qrouter-<uuid> ping -c 1 <instance ip>
* We expect this latency to be similar to the latency from not using OVS.

[Regression Potential]
* The following patch from upstream OVS solves the issue: c37d4da4f0fd0190ea8fef97399df6d27ebf6ee2. 
* It requires 755be9ea9d7250edd37e1056362e08a7436f6983 to be backported as well since the 1.4.6 still uses sysfs to get carrier info (/sys/class/net/%s/carrier) instead of ioctl. Once we are using ioctls the second patch c37d4da4f0fd0190ea8fef97399df6d27ebf6ee2 reduces the number of times the ioctl is called from netdev_get_carrier().
* There has been testing already done with these two patches applied on top of 1.4.6 in precise.

** Affects: openvswitch (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: openvswitch (Ubuntu Precise)
     Importance: Medium
     Assignee: Chris J Arges (arges)
         Status: In Progress

** Affects: openvswitch (Ubuntu Quantal)
     Importance: Medium
     Assignee: Chris J Arges (arges)
         Status: In Progress

** Also affects: openvswitch (Ubuntu Precise)
   Importance: Undecided
       Status: New

** Also affects: openvswitch (Ubuntu Quantal)
   Importance: Undecided
       Status: New

** Changed in: openvswitch (Ubuntu)
       Status: New => Fix Released

** Changed in: openvswitch (Ubuntu Precise)
     Assignee: (unassigned) => Chris J Arges (arges)

** Changed in: openvswitch (Ubuntu Quantal)
     Assignee: (unassigned) => Chris J Arges (arges)

** Changed in: openvswitch (Ubuntu Precise)
   Importance: Undecided => Medium

** Changed in: openvswitch (Ubuntu Quantal)
   Importance: Undecided => Medium

** Changed in: openvswitch (Ubuntu Precise)
       Status: New => Triaged

** Changed in: openvswitch (Ubuntu Precise)
       Status: Triaged => In Progress

** Changed in: openvswitch (Ubuntu Quantal)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1280370

Title:
  high latency between VMs in openstack using OVS

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