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    SubjectRe: [PATCH] bitops: simplify generic bit finding functions


    On Mon, 28 Apr 2008, Thomas Gleixner wrote:
    >
    > I doubt that that is worth the trouble and we should just remove those
    > inlines alltogether. This was discussed before, but Andi objected to
    > remove those micro optimizations and nobody had time to actually
    > verify the real benefits.

    Thanks for checking.

    In general, I think we should act the other way: we should *assume* that
    inlines and complex macros in header files are not worth it and we'd be
    better off with just plain function calls, unless it's really obvious that
    the inline function is always worth it.

    We have tons of good examples of inline functions in headers that really
    *really* want to be that way: <linux/list.h> is generally a collection of
    things that clearly expand to somthing that is (a) easily critical and (b)
    inlining things generally really causes a smaller code footprint than
    having a "call" instruction and all the argument setup - regardless of how
    many times it is done.

    So we do have cases where the inlines are obviously worth it. But in
    general, I think we should try to move things from the header files into
    *.c files unless there is a really clear reason for keeping it that way.

    (Some inline functions do depend on things like constant arguments goign
    away, with kmalloc() being a good example of some really nasty header file
    tricks that are likely worth it despite their extreme ugliness)

    Linus


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