Open Stack

On 1/22/2013 6:44 AM, Christopher Yeoh wrote:
> On Mon, 21 Jan 2013 15:48:52 -0500
> David Kranz <david.kranz at qrclab.com> wrote:
>
>> Attila, thanks for your comments. They are a lot to digest! I did
>> have a particular comment about the performance issue and parallelism.
>> I ran parallel nose jobs manually for the compute/servers and
>> compute/images tests and got only a little more than 1/2 the speedup
>> that should be
>> available theoretically. This was on a real machine with 24 "cpus"
>> running devstack. I believe most of the problem is due to
>> https://bugs.launchpad.net/nova/+bug/1016633 which limits the speedup
>> of parallel instance creation on a single server to half what it
>> could be.
> FWIW I see this too. Running the tempest tests with testr --parallel
> with 4 cpus I get about a 2x speed up. However with tests for most
> people taking around 30-90 minutes to run serially its quite valuable
> for developers wanting to run them regularly.
>
> Chris
I was not sneering at 2x speedup! But that is a limitation we currently 
face and I wanted to make sure every one knew it.
If we want to do better we need to either (or both):

1. Convince the nova team to fix that bug. Even if they make progress, 
there may be inherent serialization that can't be escaped.
2. Figure out which instance-creating tests
      a) do not need a "pristine" instance or one with special 
attributes, and
      b) leave the instance in a state suitable for another such test.
     Create an instance pool (local to a single parallel process) for 
such tests to use.
     I think this has been suggested before. Some of this has been done 
already by changing
     test methods in a class to reuse instances created in their class 
setup.

   -David