[GE users] Implications of Hyperthread enabled CPUs and jobs

Neil Baker neil.baker at crl.toshiba.co.uk
Thu Nov 27 09:33:27 GMT 2008


BTW, I'm not so sure which Pentium model CPUs we have installed and I don't
know how to check in Linux.  They run in Dell servers that are less than 3
years old, so are most likely more recent than Pentium 4 CPUs, but
definitely are still Hyper Threaded and not multi core CPUs.

 

Neil

 

  _____  

From: Neil Baker [mailto:neil.baker at crl.toshiba.co.uk] 
Sent: 27 November 2008 09:28
To: users at gridengine.sunsource.net
Subject: [GE users] Implications of Hyperthread enabled CPUs and jobs

 

Hi,

 

I've been reading up on Hyper-thread enabled CPUs and am wondering if it is
best to disable or enable Hyper-threading in the BIOS?

 

Most of our grid machines have 2x physical 3.0 GHz Pentium 4 CPUs with
Hyper-threading enabled.  We are running openSuse10.0 on them (BIGSMP 2.6
kernel) so they appear to be 4x logical processors.

 

If 2 jobs are assigned to run on the same machine, is the kernel or grid
engine smart enough to run them on two physically separate CPUs, or is there
a random chance that they may both run on the same physical CPU (i.e. the
main and hyper-threaded logical CPU on the same physical CPU) and therefore
leave the other physical CPU totally unused? 

 

I've read that hyper-threading only gives up to 30% more performance, so by
accidentally running 2 jobs on the same physical CPU it is going to
drastically slow these jobs down compared with running them on two separate
physical CPUs.

 

Regards

 

Neil

 

 

 


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