Messages in this thread Patch in this message | | | Date | Thu, 2 Oct 2003 14:37:55 +0300 | From | Muli Ben-Yehuda <> | Subject | Re: [PATCH] document optimizing macro for translating PROT_ to VM_ bits |
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On Tue, Sep 30, 2003 at 07:00:53PM +0900, Miles Bader wrote: > Muli Ben-Yehuda <mulix@mulix.org> writes: > > I like code that is "future proof", especially when it doesn't cost > > anything. > > Sure, it's not always worth the trouble/pain to do so unless you've > actually got some reason to think it will be mis-used. > > This is seeming more and more like such a case: it's a very special > purpose macro which is only used by two other small functions, both of > which are located immediately adjacent to the macro's definition.
After taking the time to cool down from the testosterone rush commonly induced by micro optimizations, I recon you're right. Andrew, please apply this documentation only patch against 2.6.0-t6-mm2:
--- linux-2.5/include/linux/mman.h Sun Sep 7 10:05:18 2003 +++ optimizing-macro-2.6.0-t6/include/linux/mman.h Tue Sep 30 09:47:19 2003 @@ -28,8 +28,13 @@ vm_acct_memory(-pages); } -/* Optimisation macro. */ -#define _calc_vm_trans(x,bit1,bit2) \ +/* + * Optimisation macro. It is equivalent to: + * (x & bit1) ? bit2 : 0 + * but this version is faster. + * ("bit1" and "bit2" must be single bits). + */ +#define _calc_vm_trans(x, bit1, bit2) \ ((bit1) <= (bit2) ? ((x) & (bit1)) * ((bit2) / (bit1)) \ : ((x) & (bit1)) / ((bit1) / (bit2))) -- Muli Ben-Yehuda http://www.mulix.org
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