On Tue, May 04, 2010 at 05:34:40PM -0600, Ralph Castain wrote: > > On May 4, 2010, at 4:51 PM, Gus Correa wrote: > > > Hi Ralph > > > > Ralph Castain wrote: > >> One possibility is that the sm btl might not like that you have > >> hyperthreading enabled. > > > > I remember that hyperthreading was discussed months ago, > > in the previous incarnation of this problem/thread/discussion on "Nehalem > > vs. Open MPI". > > (It sounds like one of those supreme court cases ... ) > > > > I don't really administer that machine, > > or any machine with hyperthreading, > > so I am not much familiar to the HT nitty-gritty. > > How do I turn off hyperthreading? > > Is it a BIOS or a Linux thing? > > I may try that. > > I believe it can be turned off via an admin-level cmd, but I'm not certain > about it
The challenge was too great to resist, so I yielded, and rebooted my Nehalem (Core i7 920 @ 2.67 GHz) to confirm my thoughts on the issue. Entering the BIOS setup by pressing "DEL", and "right-arrowing" over to "Advanced", then "down arrow" to "CPU configuration", I found a setting called "Intel (R) HT Technology". The help dialogue says "When Disabled only one thread per core is enabled". Mine is "Enabled", and I see 8 cpus. The Core i7, to my understanding, is a 4 core chip. Hope that helps, Douglas. -- Douglas Guptill voice: 902-461-9749 Research Assistant, LSC 4640 email: douglas.gupt...@dal.ca Oceanography Department fax: 902-494-3877 Dalhousie University Halifax, NS, B3H 4J1, Canada
