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    SubjectRe: [PATCH 11/20] Inline get_page_from_freelist() in the fast-path
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    On Wednesday 25 February 2009 00:32:53 Mel Gorman wrote:
    > On Tue, Feb 24, 2009 at 02:32:37AM +1100, Nick Piggin wrote:
    > > On Monday 23 February 2009 10:17:20 Mel Gorman wrote:
    > > > In the best-case scenario, use an inlined version of
    > > > get_page_from_freelist(). This increases the size of the text but
    > > > avoids time spent pushing arguments onto the stack.
    > >
    > > I'm quite fond of inlining ;) But it can increase register pressure as
    > > well as icache footprint as well. x86-64 isn't spilling a lot more
    > > registers to stack after these changes, is it?
    >
    > I didn't actually check that closely so I don't know for sure. Is there a
    > handier way of figuring it out than eyeballing the assembly? In the end

    I guess the 5 second check is to look at how much stack the function
    uses. OTOH I think gcc does do a reasonable job at register allocation.


    > I dropped the inline of this function anyway. It means the patches
    > reduce rather than increase text size which is a bit more clear-cut.

    Cool, clear cut patches for round 1 should help to get things moving.


    > > In which case you will get extra icache footprint. What speedup does
    > > it give in the cache-hot microbenchmark case?
    >
    > I wasn't measuring with a microbenchmark at the time of writing so I don't
    > know. I was going entirely by profile counts running kernbench and the
    > time spent running the benchmark.

    OK. Well seeing as you have dropped this for the moment, let's not
    dwell on it ;)



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