Re: [openib-general] Re: RDMA memory registration

Grant Grundler
2005-04-29T19:32:05Z

On Fri, Apr 29, 2005 at 08:22:24PM +0200, Brice Goglin wrote:
> For instance, instead of adding PROT_DONT/ALWAYSCOPY, you may use
> an ioproc hook in the fork path. This hook (a function in your driver)
> would be called for each registered page. It will decide whether
> the page should be pre-copied or not and update the registration
> table (or whatever stores address translations in the NIC).
> In addition, the driver would probably pre-copy cow pages when
> registering them.

This doesn't scale well as more cards are added to the box.
I think I understand why it's good for single cards though.

> It's nice to see these two works coming to LKML at the same time.
> It would be great if we could merge them and get a generic solution
> that's suitable to both registration based cards (IB/Myri/Ammasso)
> and MMU-based cards (Quadrics).

Aren't the mellanox mem-free cards more or less MMU's as well?
I had that impression after attending Dror Goldberg's talk
though I don't think he asserted that.
Openib.org developers conf (Feb 2005) slideset is here:
http://www.openib.org/docs/oib_wkshp_022005/memfree-hca-mellanox-dgoldenberg.pdf

Being mostly clueless about Quadrics implementation, I'm probably
missing something that makes Quadrics a MMU but not the IB variants.
Can someone clue me in please?

thanks,
grant