Re: Bloat caused by unnecessary calls to compound_head()?

From	Eric Biggers <ebiggers3@gmail.com>
Newsgroups	linux.kernel
Subject	Re: Bloat caused by unnecessary calls to compound_head()?
Date	2016-04-01 03:40 +0200
Message-ID	<riWe6-5kF-5@gated-at.bofh.it> (permalink)
References	<rh1Bg-4Nb-15@gated-at.bofh.it> <rhoRc-4ub-13@gated-at.bofh.it>
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On Sun, Mar 27, 2016 at 10:46:49PM +0300, Kirill A. Shutemov wrote:
> The idea is to introduce new type to indicate head page --
> 'struct head_page' -- it's compatible with struct page on memory layout,
> but distinct from C point of view. compound_head() should return pointer
> of that type. For the proof-of-concept I've introduced new helper --
> compound_head_t().
> 

Well, it's good for optimizing the specific case of mark_page_accessed().  I'm
more worried about the general level of bloat, since the Page* macros are used
in so many places.  And generating page-flags.h with a script is something to be
avoided if at all possible.

I wasn't following the discussion around the original page-flags patchset.  Can
you point me to a discussion of the benefits of the page "policy" checks --- why
are they suddenly needed when they weren't before?  Or any helpful comments in
the code?

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Bloat caused by unnecessary calls to compound_head()? Eric Biggers <ebiggers3@gmail.com> - 2016-03-26 20:00 +0100
  Re: Bloat caused by unnecessary calls to compound_head()? "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-03-27 21:50 +0200
    Re: Bloat caused by unnecessary calls to compound_head()? Eric Biggers <ebiggers3@gmail.com> - 2016-04-01 03:40 +0200

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