Am 06.08.2014 11:20, schrieb Le_Forgeron:
> Le 06/08/2014 10:45, clipka a écrit :
>> Must be a high-core-count thing; on my 4-core i7, running Windows 7, I
>> see this for a random scene:
>
>  From my point of view, it's a "use less than 50% of resources" thing.
> The graph goes up to 40 threads, but the guy has 80 possible cores ( 40
> true (4 x 10), x 2 by HT).
>
> The curves past 40 threads are only extension of points below 40. there
> is not even a data point at 50, 60 or 70, when Xeon are used. All 40+
> points are with Opteron (and there is no HT in Opteron... it's
> different, Intel HT and AMD module are not the same)
>
> Opteron cores' count is 48 (4 x cpu, 2 dies of 3 piledriver module each,
> each module providing 2 execution thread (core), 24 modules.

jhu correctly points to the table at the bottom:

---------------------------------------------------------------------
Selected data points showing effect of Hyper-Threading

Threads | Linux HT off | Linux HT on | Windows HT off | Windows HT on
--------|--------------|-------------|----------------|--------------
  40     | 40 sec       | 40 sec      | 53 sec         | 79 sec
  60     | 39 sec       | 35 sec      | 50 sec         | 78 sec
  80     | 39 sec       | 32 sec      | 50 sec         | 78 sec
---------------------------------------------------------------------

If it was a matter of 40 threads being poorly distributed among physical 
and virtual cores, you'd expect /some/ improvement when going to 80 
threads, but apparently there is /no/ noteworthy difference whatsoever.

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