Re: [Gelato-technical] Re: Serious performance degradation on a RAIDwith kernel 2.6.10-bk7 and later

[David Mosberger]

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@xxxxxxx> 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@xxxxxxxxxxxxxxx/msg01196.html
  >> 
  >> That would also explain why you couldn't reproduce the problem on
  >> ia32 Xeon machines.
  >> 
  >> Bartlomiej
  >> 

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