Xeon processors &&Hyper-Threading

Xeon processors &&Hyper-Threading

[Joe]

Does Linux support the Xeon (p4) processor and its capabilities?

The company I work for recently ported its application to Linux and one 
of our current HP clients asked this and I figure it would be just a 
recompile the kernel as a P4, but not sure if this would do it.

I'm not asking if Linux can RUN the Xeon processor.

I'm asking if Linux processor takes any advantage of the Hyper-Threading 
built into this processor?

below is a link to more info on this.

http://www.intel.com/design/xeon/prodbref/

Joe

Re: Xeon processors &&Hyper-Threading

[Chris Friesen]

Joe wrote:

> I'm not asking if Linux can RUN the Xeon processor.
> 
> I'm asking if Linux processor takes any advantage of the Hyper-Threading 
> built into this processor?

The kernel has full support for hyperthreading.  Be aware however that it 
doesn't always buy you any performance gain and can actually result in 
performance decrease.

Chris

-- 
Chris Friesen                    | MailStop: 043/33/F10
Nortel Networks                  | work: (613) 765-0557
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Re: Xeon processors &&Hyper-Threading

[Richard B. Johnson]

On Fri, 13 Jun 2003, Joe wrote:

> Does Linux support the Xeon (p4) processor and its capabilities?
>
> The company I work for recently ported its application to Linux and one
> of our current HP clients asked this and I figure it would be just a
> recompile the kernel as a P4, but not sure if this would do it.
>
> I'm not asking if Linux can RUN the Xeon processor.
>
> I'm asking if Linux processor takes any advantage of the Hyper-Threading
> built into this processor?
>
> below is a link to more info on this.
>
> http://www.intel.com/design/xeon/prodbref/
>
> Joe
>

You recompile the kernel for SMP as well as P4. If the motherboard
hasn't disabled HT capabilities, you will take full advantage of
the processor under Linux. Whatever "full advantage" means, is
not absolute, but whatever it is, will be used to its fullest.
Basically, if the code is I/O bound, you'll not see any difference.
If the code is compute-intensive, you will.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.

Re: Xeon processors &&Hyper-Threading

[Mark Watts]

> You recompile the kernel for SMP as well as P4. If the motherboard
> hasn't disabled HT capabilities, you will take full advantage of
> the processor under Linux. Whatever "full advantage" means, is
> not absolute, but whatever it is, will be used to its fullest.
> Basically, if the code is I/O bound, you'll not see any difference.
> If the code is compute-intensive, you will.

I discovered that you need the 'CPU Enumeration' part of ACPI to be enabled 
otherwise the kernel only sees physical processors, not sibling HT processors 
- shouldnt this be selected automatically when you select SMP ?

Re: Xeon processors &&Hyper-Threading

[Joe]

Thanks, I was asked this by one of our clients, and told them that they 
would probably have to recompile their kernel.

Joe
	

Richard B. Johnson wrote:
> On Fri, 13 Jun 2003, Joe wrote:
> 
> 
>>Does Linux support the Xeon (p4) processor and its capabilities?
>>
>>The company I work for recently ported its application to Linux and one
>>of our current HP clients asked this and I figure it would be just a
>>recompile the kernel as a P4, but not sure if this would do it.
>>
>>I'm not asking if Linux can RUN the Xeon processor.
>>
>>I'm asking if Linux processor takes any advantage of the Hyper-Threading
>>built into this processor?
>>
>>below is a link to more info on this.
>>
>>http://www.intel.com/design/xeon/prodbref/
>>
>>Joe
>>
> 
> 
> You recompile the kernel for SMP as well as P4. If the motherboard
> hasn't disabled HT capabilities, you will take full advantage of
> the processor under Linux. Whatever "full advantage" means, is
> not absolute, but whatever it is, will be used to its fullest.
> Basically, if the code is I/O bound, you'll not see any difference.
> If the code is compute-intensive, you will.
> 
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
> Why is the government concerned about the lunatic fringe? Think about it.
> 
> 

Re: Xeon processors &&Hyper-Threading

[Joe]

Don't linux vendors ship a variety of precompiled
kernels to match the various hardware scenarios?

I'm trying to imagine why a customer would ever
want or need to roll their own...

Joe

Joe wrote:

> Thanks, I was asked this by one of our clients, and told them that 
> they would probably have to recompile their kernel.
>
> Joe
>     
>
> Richard B. Johnson wrote:
>
>> On Fri, 13 Jun 2003, Joe wrote:
>>
>>
>>> Does Linux support the Xeon (p4) processor and its capabilities?
>>>
>>> The company I work for recently ported its application to Linux and one
>>> of our current HP clients asked this and I figure it would be just a
>>> recompile the kernel as a P4, but not sure if this would do it.
>>>
>>> I'm not asking if Linux can RUN the Xeon processor.
>>>
>>> I'm asking if Linux processor takes any advantage of the 
>>> Hyper-Threading
>>> built into this processor?
>>>
>>> below is a link to more info on this.
>>>
>>> http://www.intel.com/design/xeon/prodbref/
>>>
>>> Joe
>>>
>>
>>
>> You recompile the kernel for SMP as well as P4. If the motherboard
>> hasn't disabled HT capabilities, you will take full advantage of
>> the processor under Linux. Whatever "full advantage" means, is
>> not absolute, but whatever it is, will be used to its fullest.
>> Basically, if the code is I/O bound, you'll not see any difference.
>> If the code is compute-intensive, you will.
>>
>> Cheers,
>> Dick Johnson
>> Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
>> Why is the government concerned about the lunatic fringe? Think about 
>> it.
>>

Re: Xeon processors &&Hyper-Threading

[James Cleverdon]

On Saturday 14 June 2003 06:50 am, Mark Watts wrote:
> > You recompile the kernel for SMP as well as P4. If the motherboard
> > hasn't disabled HT capabilities, you will take full advantage of
> > the processor under Linux. Whatever "full advantage" means, is
> > not absolute, but whatever it is, will be used to its fullest.
> > Basically, if the code is I/O bound, you'll not see any difference.
> > If the code is compute-intensive, you will.
>
> I discovered that you need the 'CPU Enumeration' part of ACPI to be enabled
> otherwise the kernel only sees physical processors, not sibling HT
> processors - shouldnt this be selected automatically when you select SMP ?
> -

Not if you have enabled full ACPI, or if you don't have any P4s.  Some folks 
don't want any ACPI in their kernel at all.   8^)

It's possible for 'CPU Enumeration Only' to be turned on auto-magically, but 
no one has written comprehensive enough logic into the config code, yet....

-- 
James Cleverdon
IBM xSeries Linux Solutions
{jamesclv(Unix, preferred), cleverdj(Notes)} at us dot ibm dot com