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    SubjectRe: [PATCH] mm/filemap.c: unconditionally call mark_page_accessed
    On Thu, Mar 15, 2007 at 05:44:01PM +0000, Hugh Dickins wrote:
    > On Thu, 15 Mar 2007, Nick Piggin wrote:
    > > On Thu, Mar 15, 2007 at 11:56:59AM -0400, Chuck Ebbert wrote:
    > > > Ashif Harji wrote:
    > > > >
    > > > > This patch unconditionally calls mark_page_accessed to prevent pages,
    > > > > especially for small files, from being evicted from the page cache
    > > > > despite frequent access.
    > > > >
    > > > > Signed-off-by: Ashif Harji <asharji@beta.uwaterloo.ca>
    >
    > Yeah, yeah, I'm not a real mman, I don't have my own patch and
    > website for this ;) but I'm old, let me mumble some history...
    >
    > Ashif's patch would take us back to 2.4.10 when mark_page_accessed
    > was introduced: in 2.4.11 someone (probably Andrea) immediately
    > added a !offset || !filp->f_reada condition on it there, which
    > remains in 2.4 to this day. That _probably_ means that Ashif's
    > patch is suboptimal, and that your !offset patch is good.
    >
    > f_reada went away in 2.5.8, and the !offset condition remained
    > until 2.6.11, when Miquel (CC'ed) replaced it by today's prev_index
    > condition. His changelog entry appended below. Since it's Miquel
    > who removed the !offset condition, he should be consulted on its
    > reintroduction.

    Yeah I did go back and check up on that changelog, because I knew
    we had a !offset check there at one stage, which is immune to this
    problem (or at least can handle it a little better).

    I suspect that Miquel was probably more interested in _increasing_
    mark_page_accessed coverage with his new condition than restricting
    it from the !offset cases.

    Thanks for digging it up and posting here, though.
    -
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