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    SubjectRe: [PATCH 00/35] Cleanup and optimise the page allocator V3
    On Mon, Mar 16, 2009 at 12:45:55PM +0100, Nick Piggin wrote:
    > On Mon, Mar 16, 2009 at 09:45:55AM +0000, Mel Gorman wrote:
    > > Here is V3 of an attempt to cleanup and optimise the page allocator and should
    > > be ready for general testing. The page allocator is now faster (16%
    > > reduced time overall for kernbench on one machine) and it has a smaller cache
    > > footprint (16.5% less L1 cache misses and 19.5% less L2 cache misses for
    > > kernbench on one machine). The text footprint has unfortunately increased,
    > > largely due to the introduction of a form of lazy buddy merging mechanism
    > > that avoids cache misses by postponing buddy merging until a high-order
    > > allocation needs it.
    > BTW. I would feel better about this if it gets merged in stages, with
    > functional changes split out, and also code optimisations and omore
    > obvious performace improvements split out and preferably merged first.

    The ordering of the patches was such that least-controversial stuff is
    at the start of the patchset. The intention was to be able to select a
    cut-off point and say "that's enough for now"

    > At a very quick glance, the first 25 or so patches should go in first,
    > and that gives a much better base to compare subsequent functional
    > changes with.

    That's reasonable. I've requeued tests for the patchset up to 25 to see what
    that looks like. There is also a part of a later patch that reduces how much
    time is spent with interrupts disabled. I should split that out and move it
    back to within the cut-off point as something that is "obviously good".

    > Patch 18 for example is really significant, and should
    > almost be 2.6.29/-stable material IMO.

    My impression was that -stable was only for functional regressions where
    as this is really a performance thing.

    Mel Gorman
    Part-time Phd Student Linux Technology Center
    University of Limerick IBM Dublin Software Lab

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