redhat 7.3 an PE 2650 indicate 4 Processors instead 2

Les Niles lniles at Narus.com
Wed Dec 18 10:32:01 CST 2002


We have seen slightly worse performance -- on the order of 10% to 20% 
worse -- with hyperthreading enabled on a 4 CPU box dedicated to an 
application that has 2 or 3 CPU-intensive processes.  This isn't too 
surprising, since in this specialized setup there really isn't any 
work for the extra 4 CPUs created by hyperthreading.  I don't know 
if the loss of efficiency is due to the kernel or the CPUs.  

I would expect that this data point is irrelevant when there typically 
more CPU-intensive processes than physical CPUs.  

  -les  lniles at narus.com

jason andrade [mailto:jason at dstc.edu.au] wrote:
> On Wed, 18 Dec 2002, Shahram wrote:
> 
> > is this advantageous to run with Hyper-Threading on Redhat 7.3?
> 
> hyperthreading should give you an extra 25-40% of available 
> cpu depending
> on the application (multithreaded ? multiple applications?).
> 
> > is there any disadvantage known?
> 
> there hasn't been any feedback which talks about disadvantages at this
> point but it is still a relatively new piece of technology in terms of
> widespread deployment.  i am sure they will crop up.
> 
> there have been a couple of reports of people solving some stability
> issues by disabling hyperthreading but they have not been conclusive.
> 
> 
> regards,
> 
> -jason




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