[gridengine users] Questions about SGE

[Rayson Ho]

On Thu, Oct 27, 2011 at 1:01 PM, Reuti <reuti at staff.uni-marburg.de> wrote:
>> 4.  If a node is hyper-threading enabled, should we count the real core number in SGE or using the hyper-threading core number in SGE, i.e for 8-core node,  with hyper-threading, the core becomes 16.   Should SGE uses 8 or 16 in the configuration?
>
> This depends on the application. I found by some test runs that Hyperthreading will give around 1.5 times the performance for our applications but won't double it. To be on the safe side also for other applications, I turn Hyperthreading always off and use the real number of cores.

And also depends on the processor architecture...

For newer Core i7 based processors, as the processor is smarter with
hardware thread scheduling (inside the chip), you get a much better
chance of getting better job throughput (but of course each job would
run slightly slower, but not by much).

For Pentium 4 processors, just turn Hyperthreading completely off!!
Hyperthreading on the Pentium 4 can easily cause slowdown because the
*whole chip* is like a hack, see the undocumented (but existence
confirmed by an ex-Intel architect, Bob Colwell) replay feature:

http://en.wikipedia.org/wiki/Replay_system

Lastly, for memory bound HPC / fortran code, Hyperthreading almost
always won't help as memory bandwidth is the bottleneck.

Rayson




>
> -- Reuti
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