Re: [PATCHv4 00/24] THP refcounting redesign

[Aneesh Kumar K.V]

"Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> writes:

> Hello everybody,
>
> It's bug-fix update of my thp refcounting work.
>
> The goal of patchset is to make refcounting on THP pages cheaper with
> simpler semantics and allow the same THP compound page to be mapped with
> PMD and PTEs. This is required to get reasonable THP-pagecache
> implementation.
>
> With the new refcounting design it's much easier to protect against
> split_huge_page(): simple reference on a page will make you the deal.
> It makes gup_fast() implementation simpler and doesn't require
> special-case in futex code to handle tail THP pages.
>
> It should improve THP utilization over the system since splitting THP in
> one process doesn't necessary lead to splitting the page in all other
> processes have the page mapped.

I tested this patch on ppc64 and verified thp allocation and split.
I also checked the subpage_prot and it worked as expected. I will
run more tests with this series and update if I find any issues.

-aneesh

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