Re: [PATCH/RFC] Shared page tables

Ray Bryant
2006-01-23T23:58:08Z

On Tuesday 17 January 2006 17:53, Robin Holt wrote:
> Dave,
>
> This appears to work on ia64 with the attached patch. Could you
> send me any test application you think would be helpful for me
> to verify it is operating correctly?
<snip>

Dave,

Like Robin, I would appreciate a test application, or at least a description
of how to write one, or some other trick to figure out if this is working.

I scanned through this thread looking for a test application, and didn't see
one. Is it sufficient just to create a large shared read-only mmap'd file
and share it across a bunch of process to get this code invoked? How large
of a file is needed (on x86_64), assuming that we just turn on the pte level
of sharing? And what kind of alignment constraints do we end up under in
order to make the sharing happen? (My guess would be that there aren't any
such constraints (well, page alignment.. :-) if we are just sharing pte's.)

I turned on the PT_DEBUG stuff, but thus far have found no evidence of pte
sharing actually occurring in a normal system boot. I'm surprised by that as
I (naively?) would have expected shared libraries to use shared ptes.

Best Regards,
--
Ray Bryant
AMD Performance Labs Austin, Tx
512-602-0038 (o) 512-507-7807 (c)