Messages in this thread | | | From | Vernon Mauery <> | Subject | Re: kfree(NULL) | Date | Fri, 21 Apr 2006 13:30:30 -0700 |
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On Friday 21 April 2006 12:22, you wrote: > On Fri, Apr 21, 2006 at 05:07:45PM +0200, Jan Engelhardt wrote: > > >> Maybe kfree should really be a wrapper around __kfree which does the > > >> real work. Then kfree could be a inlined function or a #define that > > >> does the NULL pointer check. > > > > > >NULL pointer check in kfree saves lot of small code fragments in > > > callers. It is one of many reasons why kfree does it. > > >Making kfree inline wrapper eliminates this save. > > > > How about > > > > slab.h: > > #ifndef CONFIG_OPTIMIZING_FOR_SIZE > > static inline void kfree(const void *p) { > > if(p != NULL) > > __kfree(p); > > } > > #else > > extern void kfree(const void *); > > #endif > > > > slab.c: > > #ifdef CONFIG_OPTIMIZING_FOR_SIZE > > void kfree(const void *p) { > > if(p != NUILL) > > _kfree(p); > > } > > #endif > > > > That way, you get your time saving with -O2 and your space saving with > > -Os. > > What makes you confident that the static inline version gives a time > saving?
A static inline wrapper would mean that it wouldn't have to make a function call just to check if the pointer is NULL. A simple NULL check is faster than a function call and then a simple NULL check. In other words, there would be no pushing and popping the stack. In almost all cases, replacing an inline function with a non-inline function means a trade-off between speed and size.
--Vernon - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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