Messages in this thread | | | Date | Wed, 26 Sep 2007 20:34:49 +0200 | From | Adrian Bunk <> | Subject | Re: [PATCH 10/25] Unionfs: add un/likely conditionals on copyup ops |
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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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