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Re: [Condor-users] PASSWD_CACHE_REFRESH in 6.9.4?

	Thanks for the explanation. What is the current default and
recommended value for SCHED_UNIV_RENICE_INCREMENT in the 6.9 series?
What about adding a LOCAL_UNIV_RENICE_INCREMENT option? For example,
I would like to make the distinction that DAGMan has a higher priority
in the scheduler universe than short running user jobs in the local


On Tue, Oct 23, 2007 at 09:04:29AM -0500, Dan Bradley wrote:
> Ian Chesal wrote:
> >> This seems counter intuitive to me. Why would _not_ nice'ing 
> >> the shadow
> >> processes on a busy submit machine be a good thing?
> >>     
> >
> > Ditto. Is this a Windows scheduler only thing? I'm almost certain Alan
> > De Smet's talk every year at Condor Week talks about using higher nice
> > levels on the shadows to help out a starved-for-CPU schedd process.
> >   
> If you want to increase the priority of the schedd, that is possibly a 
> good idea.  However, using SHADOW_RENICE_INCREMENT=10 to decrease the 
> priority of the shadows below all other normal processes on the system 
> degrades throughput in every case we have observed or tested in the 6.9 
> branch.  Part of the problem is that the schedd and the shadow need to 
> communicate.  During this communication, it is actually possible for the 
> schedd to be slowed down because it is stuck waiting for a response from 
> a low priority shadow.  More common is to see connection failures in the 
> shadow logs due to the shadow being so cpu starved that it cannot form a 
> connection to the schedd, even with very generous timeouts.
> Another thing that has changed is that the 6.9.4 schedd is much less cpu 
> hungry than 6.8.  Having 10s of thousands of jobs in the queue and a few 
> thousand jobs running should not severely tax the 6.9.4 schedd on 
> reasonable server-class hardware unless the jobs are so fast that the 
> completion rate is greater than ~10-15 jobs per second.
> I'll admit that our tests of this have all been under linux and have 
> been focussed on vanilla universe.  We're certainly hoping for feedback 
> on all the other possible usage cases.
> Cheers,
> --Dan
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Stuart Anderson  anderson@xxxxxxxxxxxxxxxx