Re: Status of "ummunot" branch?

[Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 04/06/2013 23:13, Jeff Squyres (jsquyres) wrote:
> On Jun 4, 2013, at 4:50 AM, Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org> wrote:
> 
>>> Does this mean that an MPI implementation still has to register memory upon usage, and maintain its own registered memory cache?
>> Yes. However, since registration doesn't pin memory, you can leave
>> registered memory regions in the cache for longer periods, and you can
>> register larger memory regions without needing to back them with
>> physical memory.
> 
> Hmm; I'm confused.  How does this fix the MPI-needs-to-intercept-freed-memory problem?
Well, there is no problem if an application frees registered memory (in
an on-demand paging memory region) and that memory is returned to the
OS. The OS will invalidate these pages, and the HCA will no longer be
able to use them. This means that the registration cache doesn't have to
de-register memory immediately when it is freed.

Haggai
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