Re: [PATCHv5 00/28] THP refcounting redesign

[Andrew Morton]

On Fri, 24 Apr 2015 00:03:35 +0300 "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:

> Hello everybody,
> 
> Here's reworked version of my patchset. All known issues were addressed.
> 
> 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.

Are there any measurable performance improvements?

> 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.
> 
> The patchset drastically lower complexity of get_page()/put_page()
> codepaths. I encourage reviewers look on this code before-and-after to
> justify time budget on reviewing this patchset.
>
> ...
>
>  59 files changed, 1144 insertions(+), 1509 deletions(-)

It's huge.  I'm going to need help reviewing this.  Have earlier
versions been reviewed much?  Who do you believe are suitable
reviewers?
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