[GE users] Job time slowed with Hyperthreading ?

jobic jobic at polytech.univ-mrs.fr
Tue Feb 2 12:49:53 GMT 2010


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umanga wrote:
Thanks Daniel,

Could you please tell me how I can change the  number of slots this using Qmon ?

thanks
You may use the qconf -mq "partition name" command.
Then you can change the number of slots.

Yann

dagru wrote:

If you use SGE 6.2u5 the correct amount of cores and sockets
per host are reported (see qhost -cb or qstat -F m_core). When you
are using the core binding switch -binding you can let the jobs run
on complete cores (in case of hyperthreading or CMT it will be bound on all
processor numbers representing the selected cores) exclusively.
Isolating jobs from another in this way has also other advantages
like preventing cache pollution and memory access benefits.

But in any case, how many processes can actually run on the host depends
on your slot configuration and not on the amount of reported CPUs.
You may reduce the amount of slots to 4.

Cheers

Daniel

On 02/02/10 11:12, umanga wrote:


Greetings ,

Some of my execution hosts have i7 processors (4 cores with
HyperThreading ) and SGE show that each of this machine has 8 CPUs.
I noticed that similar jobs take much more time to finish on these
processors than on a processors without HT.
So I disabled HT in CMOS ,but still SGE shows 8 CPUs for this hosts.
Is there any performance issue with Hyperthreading?
How can I enable actual physical cores (4) for these hosts?

Thanks in advance.

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Yann JOBIC
HPC engineer
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