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From: Jens Maurer (Jens.Maurer_at_[hidden])
Date: 2001-08-12 14:56:12

Greg Colvin wrote:
> From: <k.hagan_at_[hidden]>
> > (Do machines with fast local stacks also have fast local heaps?)
> I don't know, as no one on this thread has mentioned any
> real machines. It would help if they did, as otherwise
> this may be a purely theoretical diversion.

Any "large" Unix machine nowadays is NUMA (non-uniform memory architecture),
i.e. there's "fast" memory (close to the CPU where the thread is currently
executing) and there's "slow" memory (close to some other CPU). This
applies to both stack and heap. Schedulers on those boxes try not to
move threads, as that penalizes future memory access, unless the memory
is moved as well.

Sun's E10000 series should be of that type, and IBM SP2 clusters
as well. (If you're addressing memory in the rack besides you, and not
on the same board, the speed of light is a definite limit on how fast
you can access it).

Also, there are concepts where some area of memory is transparently
mirrored to some other box (via a clever memory-mapped network device).
This may also count as "slow" memory.

Jens Maurer

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