On Jun 12, 2013, at 5:17 PM, Jason Gunthorpe <[email protected]> 
wrote:

> Yes, it can, via MAP_FIXED. There are lots of fun tricks you can play
> using that.


You're missing the point.

Normal users (i.e., MPI users) don't do that.  They call malloc() and they get 
what they get.

The whole point of upper-layer APIs is that they hide all the network stuff 
from the application programmer.  Verbs is *hard* for the mere mortal to 
program.  MPI can do a great deal to hide the complexities of verbs from app 
developers, but one major concession that MPI (intentionally) made is that the 
*application provides the buffer*, not MPI.

Hence, we're stuck with what buffers the user passes in.

This is the root of the whole "MPI has a registration cache" issue.

-- 
Jeff Squyres
[email protected]
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http://www.cisco.com/web/about/doing_business/legal/cri/

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