[GE users] CPU usage by array jobs

Iwona Sakrejda isakrejda at lbl.gov
Thu Jun 21 20:54:36 BST 2007


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Since this is a somehow different problem I gave it a new title.

Rayson Ho wrote:
>> Another problem I am having is that array jobs seem to be overcharged
>> when the usage is calculated (could you point me to the section of 
>> code that
>> deals with it/ I'll be happy to read it). Looks like each array job gets
>> the CPU usage of the whole array. Array jobs are very helpful but 
>> users are
>> fleeing from them in droves.....
>
> How to reproduce it?? Is it a parallel or serial job??
It happens to serial jobs. I have not done thorough studies yet, but I 
see that
usage for owners of array jobs greatly exceeds what I estimate it should be.

Also when I clear usage, then only the usage from that moment should be
taken into account - right? And I see that a user who has an array jobs, 
gets
right away usage that exceeds what he has running at that point.

Another shred of evidence is that when they switch from array jobs to
individual jobs, they get a throughput that they feel is consistent with 
their share.
If they use arrays their throughput dives.

I'll try to come with a clean example with numbers.  It is in 6.0u4 so since
I have to upgrade anyway I was postponing more studies hoping that the 
upgrade will
fix the problem. On the other hand it might not and it really increases  
the load
when instead of 1 array job with  1000 members I get 1000 jobs.....

And today I noticed that discussion about shares and CPU consumption so
I hoped the right expert might be watching and it would be easy for him 
to look at it...

Iwona

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