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SubjectRe: [Gelato-technical] Re: Serious performance degradation on a RAID with kernel 2.6.10-bk7 and later
Tony and Andrew,

I just checked 2.6.12-rc3 and the fls() fix is indeed missing. Do you
know what happened?

--david

>>>>> On Thu, 21 Apr 2005 13:30:50 +0200, Andreas Hirstius <Andreas.Hirstius@cern.ch> said:

Andreas> Hi, The fls() patch from David solves the problem :-))

Andreas> Do you have an idea, when it will be in the mainline
Andreas> kernel??

Andreas> Andreas



Andreas> Bartlomiej ZOLNIERKIEWICZ wrote:

>> 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.
>>
>> Bartlomiej
>>

Andreas> _______________________________________________
Andreas> Gelato-technical mailing list
Andreas> Gelato-technical@gelato.unsw.edu.au
Andreas> https://www.gelato.unsw.edu.au/mailman/listinfo/gelato-technical
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