"Kernel Hacking"/Developing on a HT CPU versus "physical" CPUs

[Julian Elischer]

Petri Helenius wrote:

> mre2007 at cs.columbia.edu wrote:
>
>> Dave:
>>
>> yes this makes sense! So, does the scheduler take this into 
>> consideration?
>>
>>  
>>
> The _ULE scheduler does, the _4BSD scheduler does not. 


not quite..
there is a small sysctl that will try make it select a processor on an 
idle die
when selecting which idle cpu to wake up next..
but it's turned off by default and it doesn;t seem to make much difference..
(It' s also a hack because it's hard-wired for 2vcpus /die).. it is more 
a proff of concept
hack.. (which is why  it is turned off))

>
>
> Pete
>
>> -Marc
>>
>>  
>>
>>> Here is one example:
>>> If you have dual HT processors, this looks like 4 CPUs to the O/S.
>>> For performance reasons, the scheduler should not treat them equally.
>>> If there are two threads to run, they should be put on different 
>>> physical
>>> processors (vs. two hyperthreads of the same processor).
>>>
>>>
>>> David Dolson (ddolson at sandvine.com, www.sandvine.com)
>>>
>>>
>>>   
>>>
>>>> -----Original Message-----
>>>> From: owner-freebsd-smp at freebsd.org
>>>> [mailto:owner-freebsd-smp at freebsd.org]On Behalf Of
>>>> mre2007 at cs.columbia.edu
>>>> Sent: Saturday, September 25, 2004 10:48 AM
>>>> To: freebsd-smp at freebsd.org
>>>> Subject: "Kernel Hacking"/Developing on a HT CPU versus
>>>> "physical" CPUs
>>>>
>>>>
>>>> Hey, I was wondering if from a developing/"kernel hacking"
>>>> standpoint, are
>>>> hyperthreading and two "physical" CPUs any different? At what
>>>> point do the
>>>> differences have to be taken into consideration when working on the
>>>> FreeBSD kernel/scheduler/etc? I'm looking to start contributing to the
>>>> FreeBSD project and am trying to get some hardware set aside.
>>>>
>>>> Thanks!
>>>> -Marc
>>>> _______________________________________________
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>>>>
>>>>     
>>>
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>>  
>>
>
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