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Re: [Condor-users] Preemption question

The newer condor manual actually describes the things considered for
pre-emption and the order that they are done in.  First thing
to look at is value of PREEMPTION_REQUIREMENTS.  IF not false,
then jobs from a high priority user can trump those of a low priority user.


Steven C. Timm, Ph.D  (630) 840-8525  timm@xxxxxxxx  http://home.fnal.gov/~timm/
Fermilab Computing Div/Core Support Services Dept./Scientific Computing Section
Assistant Group Leader, Farms and Clustered Systems Group
Lead of Computing Farms Team

On Fri, 30 Jun 2006, Miskell, Craig wrote:

	To follow on from the "Preemption question" thread of March this
l), I have run into an interesting situation.
I, too, thought I had disabled pre-emption with:
PREEMPT                 = FALSE

Lo and behold, some jobs got pre-empted last night (the first time my
pool has had any real contention for resources).  From my reading of the
previous thread, this can potentially happen when PREEMPT is false, but
only if the machine has a RANK expression which results in it preferring
a different job to the one currently running.  If that understanding is
correct, then something weird is going on, as all my startds have a Rank
of 0 (I've done nothing special).

Interestingly, in this case the preferred/pre-empting job had a Rank =
Mips, whereas the pre-empted/evicted job had a Rank of 0.  This may be a
red-herring, but does seem suspiciously related.  Should the job Rank
have any effect on preemption (I would have thought it wouldn't even be
considered until the Negotiator had decided that a given Startd was a
candidate for satisfying the claim).

I'm going to set MaxJobRetirementTime to something large as a
pre-emptive (pun intended) strike against such things happening again,
but I'm curious as to why this might have happened at all, as it
indicates a lack of understanding on my part.

Condor version is 6.7.18, running on linux (x86_64 and i386).

Craig Miskell,
Technical Support,
AgResearch Invermay
03 489-9279
"Cynical" is a term invented by optimists to describe realists.
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