[Bug 566715] [NEW] GREEDY scheduling policy occasionally over-subscribes nodes (more VMs than cores)

[Piotr T Zbiegiel]

Public bug reported:

We are running eucalyptus 1.6.2-0ubuntu27 on lucid beta1.  I will retest
this bug on the latest-and-greatest as soon as that is feasible on our
cluster.

We have been running many tests with the ROUNDROBIN scheduling policy.
As a test I changed it to GREEDY a little over a week ago.  The
scheduling policy seems to work as expected except that occasionally
when servicing large requests the cluster controller will request that a
node run more VMs than available cores on a machine.  We are using kvm.
When making a large request (say 100 VMs) it seems that invariably one
of the nodes used to run the machines will be over-subscribed.  Our
machines have 8 cores each and I often see 9 VMs and occasionally I've
seen as many as 12.

I have checked that the machines with extra VMs did not have hyper-
threading enabled and were therefore reporting the correct number of
cores to Eucalyptus according to the
/var/log/eucalyptus/euca_test_nc.log file on each system.

** Affects: eucalyptus (Ubuntu)
     Importance: Undecided
         Status: New

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GREEDY scheduling policy occasionally over-subscribes nodes (more VMs than cores)
https://bugs.launchpad.net/bugs/566715
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