Serge E. Hallyn writes: > While investigating the inordinate performance impact one of my patches > seemed to be having, we tracked it down to two hlist_for_each_entry > loops, and finally to the prefetch instruction in the loop.
I would be interested to know what results you get if you leave the loops using hlist_for_each_entry but change prefetch() and prefetchw() to do the dcbt or dcbtst instruction only if the address is non-zero, like this: static inline void prefetch(const void *x) { if (x) __asm__ __volatile__ ("dcbt 0,%0" : : "r" (x)); } static inline void prefetchw(const void *x) { if (x) __asm__ __volatile__ ("dcbtst 0,%0" : : "r" (x)); } It seems that doing a prefetch on a NULL pointer, while it doesn't cause a fault, does waste time looking for a translation of the zero address. Paul. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/