On Sat, 25 Mar 2006, Alex Izvorski wrote:

 http://linuxraid.pastebin.com/621363 - oprofile annotated assembly

it looks to me like a lot of time is spent in __find_stripe() ... i wonder 
if the hash is working properly.

in raid5.c you could try changing

#define stripe_hash(conf, sect) (&((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK]))

to

#define stripe_hash(conf, sect) (&((conf)->stripe_hashtbl[(((sect) >> STRIPE_SHIFT) ^ ((sect) >> (2*STRIPE_SHIFT))) & HASH_MASK]))

or maybe try using jhash_1word((sect) >> STRIPE_SHIFT, 0) ...

-dean