[openib-general] Re: Question about pinning memory

[Jeff Squyres]

On Jul 24, 2005, at 4:41 AM, Michael S. Tsirkin wrote:

>> Internal table lookup is a search in balanced tree. Hardware memory
>> registration is system call + writes on PCI bus + search in balanced
>> tree in get_user_pages,
>
> I cant tell without seeing actual benchmarks.
> Certainly tricks like overriding malloc/free operations can have
> impact on overall application performance.

I do not have a microbenchmark showing that pinning is expensive -- I'm 
actually not the guy doing Open IB work in Open MPI (Tim Woodall and 
Galen Shipman are).  However, several of us were talking about this 
problem, and it was suggested that we ask the openib-general list, so I 
posted.

I can ask Tim and Galen to hack up some microbenchmarks.

FWIW, Open MPI has an option that does something similar to what was 
previously described -- balanced table lookups to see if memory is 
pinned, etc.

-- 
{+} Jeff Squyres
{+} The Open MPI Project
{+} http://www.open-mpi.org/