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    SubjectRe: [PATCH 10/25] Unionfs: add un/likely conditionals on copyup ops
    On Wed, Sep 26, 2007 at 09:40:20AM -0400, Erez Zadok wrote:
    >...
    > Also, Auke, if indeed compilers are [sic] likely to do better than
    > programmers adding un/likely wrappers, then why do we still support that in
    > the kernel? (Working for a company tat produces high-quality compilers, you
    > may know the answer better.)
    >
    > Personally I'm not too fond of what those wrappers do the code: they make it
    > a bit harder to read the code (yet another extra set of parentheses); and
    > they cause the code to be indented further to the right, which you sometimes
    > have to split to multiple lines to avoid going over 80 chars.

    There are some places in generic code where it makes sense, e.g.:
    #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while(0)

    If you run into a BUG() it's anyway game over.

    And there are some rare hotpaths in the kernel where it might make
    sense, and many other places where the likely/unlikely usage that might
    be present doesn't make sense.

    Unless you know you need it you simply shouldn't use likely/unlikely.

    > Cheers,
    > Erez.

    cu
    Adrian

    --

    "Is there not promise of rain?" Ling Tan asked suddenly out
    of the darkness. There had been need of rain for many days.
    "Only a promise," Lao Er said.
    Pearl S. Buck - Dragon Seed

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