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Nathen 10-03-2010 12:21 AM

Debian hyperthreading support
 
Thanks for replying. The system is running mainly a file server so
it's not very CPU-intensive, I wanted to be sure I wasn't wasting
performance by having it enabled, for example.
Thanks


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Mark Allums 10-03-2010 01:42 AM

Debian hyperthreading support
 
On 10/2/2010 6:08 PM, Nathen wrote:

Pretty simple question really, does Debian i.e. the current Linux
Kernel handle hyperthreading well? I have a server running on an Intel
Atom D510, should I have HT enabled or disabled to get the best
performance?
Thanks. :)





Recently (kernel 2.6.31 or so) there has been a separate kernel
configuration option to optimize for SMT (Intel's word for it is
"hyperthreading"). Separate from SMP (multiple processor). Under SMT,
a single core running two threads looks like two cores to most of the
kernel itself and to user programs. This has been true for a long time.
Only now, there is more support and optimization for it. If your
kernel has it enabled, some workloads won't see any difference, but some
will benefit a lot. I think it is enabled by default in the most recent
stock kernels (please correct me if I'm wrong.)


Note, you may need to enable hyperthreading in your BIOS, as well.

I would enable it for Core i7 and Atom. P4-era machines could sometimes
have software compatibility issues with it enabled, but I think Debian
and Atoms are good.







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Camaleón 10-03-2010 12:13 PM

Debian hyperthreading support
 
On Sun, 03 Oct 2010 01:21:33 +0100, Nathen wrote:

> Thanks for replying. The system is running mainly a file server so it's
> not very CPU-intensive, I wanted to be sure I wasn't wasting performance
> by having it enabled, for example. Thanks

I don't think you are going to get any penalty in performance by using a
kernel with HT enabled (in fact, that could have happened for some P4
featuring the "replay system" but I fairly doubt it is still live in Atom
based CPUs) :-?

Greetings,

--
Camaleón


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Arnt Karlsen 10-24-2010 07:07 PM

Debian hyperthreading support
 
On Sat, 02 Oct 2010 20:42:01 -0500, Mark wrote in message
<4CA7DF69.7040306@allums.com>:

> On 10/2/2010 6:08 PM, Nathen wrote:
> > Pretty simple question really, does Debian i.e. the current Linux
> > Kernel handle hyperthreading well? I have a server running on an
> > Intel Atom D510, should I have HT enabled or disabled to get the
> > best performance?
> > Thanks. :)
> >
> >
>
>
> Recently (kernel 2.6.31 or so) there has been a separate kernel
> configuration option to optimize for SMT (Intel's word for it is
> "hyperthreading"). Separate from SMP (multiple processor). Under
> SMT, a single core running two threads looks like two cores to most
> of the kernel itself and to user programs. This has been true for a
> long time. Only now, there is more support and optimization for it.
> If your kernel has it enabled, some workloads won't see any
> difference, but some will benefit a lot. I think it is enabled by
> default in the most recent stock kernels (please correct me if I'm
> wrong.)
>
> Note, you may need to enable hyperthreading in your BIOS, as well.
>
> I would enable it for Core i7 and Atom. P4-era machines could
> sometimes have software compatibility issues with it enabled,

..details, please, I'm trying to figure out what I did wrong in
my X|dri|etc setup on my FlightGear P4.

> but I think Debian and Atoms are good.

--
..med vennlig hilsen = with Kind Regards from Arnt... ;o)
...with a number of polar bear hunters in his ancestry...
Scenarios always come in sets of three:
best case, worst case, and just in case.


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