[Beowulf] single machine with 500 GB of RAM

Vincent Diepeveen diep at xs4all.nl
Wed Jan 9 05:32:31 PST 2013


Take a good look at the code.
You can probably get a better IPC out of it with a few cores by using  
a tricky form of parallellisation.
Yet then it stops as far as parallellization is concerned :)



On Jan 9, 2013, at 2:05 PM, Jörg Saßmannshausen wrote:

> Hi John,
>
> I was toying with this idea as well. However, what I do not know  
> is: as it is
> a single core job, do I really need the second CPU for the memory  
> management
> or would that slow down things? In other words, does it look like  
> that:
> Memoryrequest CPU#0 -> CPU#1 -> RAM
> So if I am using a single socket motherboard, would that not be  
> faster or does
> a single CPU not cope with that amount of memory?
>
> Regards
>
> Jörg
>
> On Wednesday 09 January 2013 12:53:41 you wrote:
>> You will need to populate all of the CPU sockets if you are filing  
>> all the
>> DIMM slots.
>> So yoy probably need more than one CPU
>> On Jan 9, 2013 12:42 PM, "Jörg Saßmannshausen"
>> <j.sassmannshausen at ucl.ac.uk>
>>
>> wrote:
>>> Dear all,
>>>
>>> Happy New Year!
>>>
>>> I was wondering whether people on the list here have some first hand
>>> experiences with this. I have been asked to purchase a single  
>>> machine
>>> with around 500 GB of RAM. We would not need more than 8 cores  
>>> here. The
>>> job
>>
>> simply
>>
>>> needs that much of memory (and even then it is running for 14 days).
>>>
>>> Now, with that amount of memory used by a single core, I would have
>>
>> thought
>>
>>> that I need a fast memory interconnect, i.e. a high memory  
>>> bandwidth. I
>>
>> was
>>
>>> thinking of getting an Intel Sandybridge CPU (maybe a  E5-2650)  
>>> for that
>>> machine and get a motherboard with can cope with that amount of  
>>> memory.
>>
>> Does
>>
>>> anybody happen to have some recommendations here or knows of  
>>> potential
>>> pitfalls?
>>>
>>> Also, in a related problem, how would I set the kernel.shmmni,
>>
>> kernel.shmall
>>
>>> and kernel.shmmax values so I am not running out of memory  
>>> handles here.
>>
>> I am
>>
>>> still confused by that.
>>>
>>> Any kind of advice here is much appreciated. Given it is an  
>>> expensive
>>
>> piece of
>>
>>> hardware we want to purchase I want to get it right.
>>>
>>> All the best from a grey London
>>>
>>> Jörg
>>>
>>> --
>>> *************************************************************
>>> Jörg Saßmannshausen
>>> University College London
>>> Department of Chemistry
>>> Gordon Street
>>> London
>>> WC1H 0AJ
>>>
>>> email: j.sassmannshausen at ucl.ac.uk
>>> web: http://sassy.formativ.net
>>>
>>> Please avoid sending me Word or PowerPoint attachments.
>>> See http://www.gnu.org/philosophy/no-word-attachments.html
>>>
>>> _______________________________________________
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>>> Computing
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>>
>> http://www.beowulf.org/mailman/listinfo/beowulf
>
> -- 
> *************************************************************
> Jörg Saßmannshausen
> University College London
> Department of Chemistry
> Gordon Street
> London
> WC1H 0AJ
>
> email: j.sassmannshausen at ucl.ac.uk
> web: http://sassy.formativ.net
>
> Please avoid sending me Word or PowerPoint attachments.
> See http://www.gnu.org/philosophy/no-word-attachments.html
>
> _______________________________________________
> Beowulf mailing list, Beowulf at beowulf.org sponsored by Penguin  
> Computing
> To change your subscription (digest mode or unsubscribe) visit  
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