[Condor-users] Avoiding preemption ping-pong

[Martin Billinger <martin.billinger@xxxxxxxxx>]

Hi there,

I have recently observed the jobs of two users keep preempting each 
other every few hours.

We are running a small condor pool with some dedicated machines.
Two users have submitted a large number of long running jobs. Both users 
have roughly the same priority.

Now, what happens is that first one of the users gets assigned all 
available resources. Once EUPs differ by 20%, all of that users' jobs 
are preempted and the other user gets all resources. This repeats every 
few hours and causes many cycles to be lost.


I believe preemption could be restricted by taking actual resource usage 
into account. Something like this might work in the two user case:
PREEMPTION_REQUIREMENTS = RemoteUserPrio/RemoteUserResourcesInUse > 
TARGET.SubmitterUserPrio/TARGET.SubmitterUserResourcesInUse


Is it possible to implement a 'fair' and efficient preemption strategy 
for an arbitrary number of users? Any thoughts appreciated!

Thanks in advance,
Martin