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    SubjectRe: [PATCH -mm] vmscan: make mapped executable pages the first class citizen
    On Fri, 8 May 2009 23:00:45 +0100
    Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

    > > The patch seems reasonable but the changelog and the (non-existent)
    > > design documentation could do with a touch-up.
    >
    > Is it right that I as a user can do things like mmap my database
    > PROT_EXEC to get better database numbers by making other
    > stuff swap first ?
    >
    > You seem to be giving everyone a "nice my process up" hack.

    Yep.

    But prior to 2.6.27(?) the same effect could be had by mmap()ing the
    file with or without PROT_EXEC. The patch restores a
    probably-beneficial heuristic which got lost in the LRU rewrite.

    So we're no worse than pre-2.6.27 kernels here. Plus there are
    probably more effective ways of getting that sort of boost, such as
    having a process running which simply touches your favoured pages
    at a suitable (and fairly low) frequency.


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