[ofa-general] Re: [ewg] Re: [OMPI devel] Re: OMPI over ofed udapl - bugs opened

[Gleb Natapov]

On Thu, May 10, 2007 at 05:56:13PM +0300, Michael S. Tsirkin wrote:
> > Quoting Jeff Squyres <jsquyres at cisco.com>:
> > Subject: Re: [ewg] Re: [OMPI devel] Re: OMPI over ofed?udapl -?bugs?opened
> > 
> > On May 10, 2007, at 10:28 AM, Michael S. Tsirkin wrote:
> > 
> > >>What is the advantage of this approach?
> > >
> > >Current ipoib cm uses this approach to simplify the implementation.
> > >Overhead seems insignificant.
> > 
> > I think MPI's requirements are a bit different than IPoIB.  See  
> > Gleb's response. It is not uncommon for MPI apps to have connections  
> > open to many peers simultaneously.
> 
> You mean, hundreds of QPs between the same pair of hosts?
> Yes, in this case you might start running out of QPs.

Why is it matters that QPs between the same pair of hosts or not.
QPs are global resource, aren't they?

> 
> > Registered memory / internal  
> > buffering usage is a Big Deal in the MPI / HPC community.
> 
> I don't see the connection with the # of QPs.
> They are very cheap in memory.
> 
4K is cheap?

--
			Gleb.