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Subject: Re: [OMPI users] Shared Memory (SM) module and shared cache implications
From: Simone Pellegrini (spellegrini_at_[hidden])
Date: 2009-06-25 08:31:04

Ralph Castain wrote:
> At the moment, I believe the answer is the main memory route. We have
> a project just starting here (LANL) to implement the cache-level
> exchange, but it won't be ready for release for awhile.
Interesting, actually I am a PhD student and my topic is optimization of
MPI applications on multi-core architectures. I will be very interested
in collaborating in such project. Can you give me more details about it

regards, Simone
> On Jun 25, 2009, at 2:39 AM, Simone Pellegrini wrote:
>> Hello,
>> I have a simple question for the shared memory (sm) module developers
>> of Open MPI.
>> In the current implementation, is there any advantage of having
>> shared cache among processes communicating?
>> For example let say we have P1 and P2 placed in the same CPU on 2
>> different physical cores with shared cache, P1 wants to send a
>> message to P2 and the message is already in the cache.
>> How the message is being actually exchanged? Is the cache line
>> invalidated, written to main memory and exchanged by using some DMA
>> transfer... or is the message in the cache used (avoiding access to
>> the main memory)?
>> thanks in advance, Simone P.
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