[MPICH] Can I ask MPI to not copy the data to shared-mem ?

[Darius Buntinas]

Yeah, interesting.  But you have to read the maps file every time you do 
a send or receive.  You can't just read the maps file once at init and 
cache it, because the user could change the mapping after init.

I guess for sufficiently large messages the benefit of not having to 
copy would outweigh the cost of reading the maps file.

It may be an interesting study.

-d

On 10/09/2007 02:54 PM, Jean-Marc Saffroy wrote:
> On Tue, 9 Oct 2007, Darius Buntinas wrote:
> 
>> Hmm.  I can't see a way that an MPI implementation could (efficiently 
>> and reliably) check that two virtual addresses from different 
>> processes point to the same location in a shared memory region.  An 
>> MPI implementation wouldn't have enough information to do what you're 
>> asking.
> 
> It could very well have this information from the operating system.
> On Linux, /proc/self/maps has all the required details.
> 
>