Re: Folios for anonymous memory

[Ryan Roberts <ryan.roberts@arm.com>]

Thanks for the fast response - I appreciate it!

>>
>> - I’ve seen folios for anon memory listed as future work; what’s the current
>> status? Is anyone looking at this? It’s something that I would be interested to
>> take a look at if not (although don’t take that as an actual commitment yet!).
>
> There are definitely people _looking_ at it.  I don't think anyone's
> committed to it, and I don't think there's anyone 50 patches into a 100
> patch series to make it work ;-)  I think there are a lot of unanswered
> questions about how best to do it.

Is there any list outlining those questions? Having had a quick look at
do_anonymous_page(), which is where a bunch of my overheads seem to be coming
in, (and having the luxury of not being intimately familiar with mm ;-) ) it
looks like it would be doable to convert it to allocate order-2 folios, for
example. I guess a lot of the difficulty is in figuring out heuristics for
choosing the right folio size for a given fault? And then thinking about handing
COW, swap, parallel faults, etc?


> I don't want you to get the impression that all the work going on is
> targetted at filesystem folios.  There's a lot of infrastructure that's
> being converted from pages to folios and being reexamined at the same
> time to be sure it handles arbitrary-order folios correctly.  Right
> now, I'm working on the architecture support for inserting multiple
> consecutive PTEs at the same time:
> https://lore.kernel.org/linux-arch/20230211033948.891959-1-willy@infradead.org/

Yep - I'm aware of that, thanks!

>
> Thanks for reaching out.  We have a Zoom call on alternate Fridays,
> so if you're free at 5pm UK time (yes, I know ... trying to fit in both
> California and central Europe leads to awkward times for phone calls),
> I can send you the meeting details.

Yes, I'd be keen to join, although not the easiest time for me. I can't do this
week, but would like to join on an ad-hoc basis if that's ok? When is the next call?

Thanks,
Ryan

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