Re: [condor-users] job priority question

[Alain Roy <roy@xxxxxxxxxxx>]

Colin Devine wrote:
> We have recently installed Condor here and I have a question about users
> job priority.  When submitting jobs to condor some users have jobs with a
> 10 priority run while jobs with a 0 priority wait in the queue, which is
> the expected behavior.  They also have jobs with a 0 priority run while
> jobs with a 10 priority wait in the queue which is the opposite what is
> expected.

Colin, are you talking about the job priorities that are set by the user on 
a per-job basis? I think so, but I just want to clarify that you aren't 
talking about user priorities.

From your description, a couple of things could be happening.

1) These are priorities per-user. If there are two users, Condor will first 
pick a user that can run jobs, then pick a job for that user. It does not 
look at the job priorities when picking a user, so job priorities will only 
affect the order in which a single users's jobs are run with respect to 
each other, but not the order in which jobs are run with respect to other 
users.

2) For a single user, just because one job has a higher priority than 
another does not mean that it will run first. This is because jobs can have 
different requirements, and the higher priority job may not be able to run 
as soon as the lower priority job.  Here's a simple example: if you have a 
high priority job that requires Linux and a low priority job that requires 
Windows, but no Linux computers are available, then the Windows job may run 
first. More subtle requirement differences may also have an impact.

> Can anyone explain to me what might be causing this?  Should higher
> priority jobs preempt lower priority jobs of the same user?

Job priorities do not preempt running jobs, they only affect the order in 
which jobs are started.

If this doesn't answer your question, it's always possible you've found a 
real bug...

-alain


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