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Just out of idle curiosity, will 3.7 have special support for
processor groups? As far as I understand this will be required
under Windows if an application wishes to make use of more than
64 logical cores ;) It's not *that* far-fetched really, you
could already get 64 logical cores today with four of these:
http://www.intel.com/p/en_US/products/server/processor/xeon7000/
Given the release cycle of POV-Ray it is likely that 3.7 will
be used on such systems before the next version is out.
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On Tue, 04 May 2010 14:14:50 +0200, Warp <war### [at] tag povrayorg> wrote:
> Christian Froeschlin <chr### [at] chrfrde> wrote:
>> As far as I understand this will be required
>> under Windows if an application wishes to make use of more than
>> 64 logical cores
>
> Why?
Windows clusters processors into groups of no more than 64 in each group
for performance reasons.
More information here (Yes, this is the "I feel lucky" link):
http://msdn.microsoft.com/en-us/library/dd405503(VS.85).aspx
--
FE
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Le 04/05/2010 15:47, Fredrik Eriksson nous fit lire :
> On Tue, 04 May 2010 14:14:50 +0200, Warp <war### [at] tagpovrayorg> wrote:
>> Christian Froeschlin <chr### [at] chrfrde> wrote:
>>> As far as I understand this will be required
>>> under Windows if an application wishes to make use of more than
>>> 64 logical cores
>>
>> Why?
>
> Windows clusters processors into groups of no more than 64 in each group
> for performance reasons.
Tsss.
So, because the ms-os scheduler is flawed (and might not scale fine on
high number of processors (including pseudo-cores of HT), as well as
they have a limited API interface), they are reporting the usage of more
than one group to the applications.
Remind me of (non-)multitasking... the microsoft way in windows 3.
I like the marketing-bs about hot-pluggable processors and the
reservation of room in groups, and yet making groups as big as
possible... laughable.
Notice: you need a 64-bit version of 7 or 2008R2...
And for a lot of memory, you need the higher (more expensive) versions
(for just a registry change... AFAIK)
Well, given the hardware cost per cpu (even with 8 cores/16 HT) and the
others parts, it might be a fine line in the pricelist.
But on such hardware, usually, you use virtualisation at its best,
running windows only as a VM, not the main (barebone) OS. Chances are
windows won't get to see all the processors at once anyway.
Now, if someone wants to prove me wrong and offer me a 256-way xeon 7500
machine, fully loaded with processors, memory, and all, just feel
free... I would install Linux in it (bigiron kernel), and might need
some more money for the electricity bild (and cooling).
I'm afraid the graphic card will be horrible.
I would stand by: source of povray are available, if you have such a
computer, and wants full povray on it, you might as well perform the
fine tuning of the code for the actual setting. Then share it with the
pov-team!
Note also, MS-way: groups are not backward compatible with Vista, 2008,
2003, XP...
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Christian Froeschlin <chr### [at] chrfrde> wrote:
> Fredrik Eriksson wrote:
> > Windows clusters processors into groups of no more than 64 in each group
> > for performance reasons.
> there are also some restrictions in the classic api such as the
> integer bitmask for thread affinities which only has so many bits.
> On a 32-bit system the limit is 32 logical cores. Probably a case
> of "32 cores ought to be enough for everybody" ;)
My wild guess is that since the kernel of Windows NT had huge problems
dealing with even 16 CPUs, and since the kernel of Windows XP and newer
are based on NT, they have developed the multiprocessor routines a bit
further, but are probably still hitting some efficiency limits somewhere
at 64 CPUs.
It's not like it's impossible to write a multitasking operating system
which can efficiently scale up even to thousands of CPUs. Many Unix
operating systems which were built from the very beginning to handle
multiple CPUs are very efficient at it. (If I'm not mistaken, Sun Solaris
is one example. I have heard that it can easily handle 2048 CPUs and even
more, without any significant overhead.)
--
- Warp
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