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    SubjectRe: mm, page_alloc: Swap likely to unlikely as code logic is different for next_zones_zonelist()
    On Fri, 6 Jan 2017 09:00:23 +0100
    Vlastimil Babka <vbabka@suse.cz> wrote:

    > On 01/06/2017 02:01 AM, Steven Rostedt wrote:
    > > Commit 682a3385e773 "mm, page_alloc: inline the fast path of the
    > > zonelist iterator" changed how next_zones_zonelist() is called, by
    > > adding a static inline function to do the fast path. This function adds:
    > >
    > > if (likely(!nodes && zonelist_zone_idx(z) <= highest_zoneidx))
    >
    > Your profiling stats posted online suggested even this one was wrong:
    >
    > function.file.line correct incorrect percent
    > next_zones_zonelist.mmzone.h.965 216840653 25415261543 %0.85
    >
    > Was it bogus then, or is there other explanation? I have speculated that
    > this might be due to multiple cpusets configured in the system.

    I didn't have any cpusets configured on either system.

    But the number is exaggerated, as it too was affected by the "constant"
    optimization by gcc. But when I fixed that, it still gives me about
    50%. Probably best just to remove the likely() in that case.

    > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    >
    > Anyway this makes sense.
    >
    > Acked-by: Vlastimil Babka <vbabka@suse.cz>

    Thanks!

    -- Steve

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