[Pw_forum] Insufficient Virtual Memory

[Axel Kohlmeyer]

On Fri, 27 Feb 2009, Vo, Trinh wrote:

VT> Dear Axel,
VT> 
VT> Thanks for clarification.
VT> 

VT> About the benchmarks, I just simply to see how well is the 
VT> performance of the cluster we bought in term of scaling with QE.  I 
VT> sent some plots to you, but the email did not go thru because of the 
VT> restriction of the size (larger than 40K).

please send it to me personally.

VT> Currently, I am not happy at the fact that the difference in CPU 
VT> time and wall time is too large.  When I run a longer job, which 

what kind of hardware do you have, how much memory,
and what kind of interconnect do you have?

VT> took ~2h CPU time long, the wall time was ~7h when I run from the 
VT> head node, and ~4h when I run from another node, which is not the 
VT> head node.  The reason why I avoided running from the head node was 
VT> that other users might use the head node to do their work, causing 
VT> the long wall time.  Even when I did the test runs (short runs), 
VT> when no one used the cluster, the difference was still up to 25%, 
VT> depending on how many nodes I used. I do not know what I should do 
VT> to improve this difference. According to you, what should I look at 
VT> to fix the problem. (I also need to read the forum discussion as 
VT> Lorenzo said in his email).

how should the number of users on the machine affect the performance?
don't you use a batch system to regulate access to the nodes?

cheers,
   axel.


VT> 
VT> Thanks,
VT> 
VT> Trinh
VT> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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If you make something idiot-proof, the universe creates a better idiot.