Messages in this thread | | | Date | Thu, 21 Apr 2005 11:42:31 +0200 | From | Bartlomiej ZOLNIERKIEWICZ <> | Subject | Re: Serious performance degradation on a RAID with kernel 2.6.10-bk7 and later |
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Hi!
> A small update. > > Patching mm/filemap.c is not necessary in order to get the improved > performance! > It's sufficient to remove roundup_pow_of_two from |get_init_ra_size ... > > So a simple one-liner changes to picture dramatically. > But why ?!?!?
roundup_pow_of_two() uses fls() and ia64 has buggy fls() implementation [ seems that David fixed it but patch is not in the mainline yet]:
http://www.mail-archive.com/linux-ia64@vger.kernel.org/msg01196.html
That would also explain why you couldn't reproduce the problem on ia32 Xeon machines.
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