[GE users] Correct Way to Reduce Number of Slots?

jlforrest jlforrest at berkeley.edu
Wed Jan 6 19:57:50 GMT 2010

I have a pseudo-cluster of 12 dual processor
Mac Pros all running Mac OS 10.5 and SGE 6.2u4.
(I say pseudo-cluster because these Macs
are also being used as desktop machines
for grad students).

3 of these Mac Pros are newer than the rest,
and have dual Nehalem processors which support
hyperthreading. This makes them look like they
have 16 cores, but they really only have 8.

SGE correctly sees 16 CPUs and slots on these
3 Macs. However, the users don't like this because
it means that although these machines can run twice
as many jobs as the other Macs, each job takes
twice as long to finish. Seeing results sooner
is more important to them then seeing lots of results.

So, I tried to modify my SGE configuration so that
SGE would only see 8 slots on these Macs. I ran
'qconf -mconf all.q' and changed the number of
slots for the 3 Macs to 8. This kind of worked,
as shown by the following line of output from

all.q at xxx.cchem.berkeley.ed BIP  0/15/8  15.13 darwin-x86

There are 15 slots in use because they were in use before
I made the change. The total number of slots reflects
the change I made.

However, when I run 'qmon' and look at the Queue Control->
Hosts page, the "#CPU" column still shows 16. I was
expecting this to also show 8.

What am I doing wrong? Is there a better way to do

Jon Forrest
Research Computing Support
College of Chemistry
173 Tan Hall
University of California Berkeley
Berkeley, CA
jlforrest at berkeley.edu


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