Date: Thu, 31 Mar 2016 20:33:29 -0500
From: Eric Biggers <ebiggers3@gmail.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        kirill.shutemov@linux.intel.com, Hugh Dickins <hughd@google.com>
Subject: Re: Bloat caused by unnecessary calls to compound_head()?
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 <20160327194649.GA9638@node.shutemov.name>
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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?