Open Stack

So this is from extensive study of just raw hardware and the effects of hyperthread not in a virtualized environment..

hyperthreading isnt context switching, so there really isnt ever any down side computationally to having it turned on.

some codes it helps on, some codes you dont notice its there. At best we saw 20% runtime decrease due to it being on.

That being said for us on real raw hardware the increase in power used with it on outweighs the performance gain.  

So we mostly want it off for that reason.

s

-- 
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 Steve Heistand                           NASA Ames Research Center
 SciCon Group                             Mail Stop 258-6
 steve.heistand at nasa.gov  (650) 604-4369  Moffett Field, CA 94035-1000
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 "Any opinions expressed are those of our alien overlords, not my own."



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