Re: [Bugme-new] [Bug 40262] New: PROBLEM: I/O storm from hell on kernel 3.0.0 when touch swap (swapfile or partition)

[Steffen Michalke <StMichalke@web.de>]

Am Montag, den 29.08.2011, 09:01 +0900 schrieb KAMEZAWA Hiroyuki: 
> On Sun, 28 Aug 2011 15:13:35 +0400
> Konstantin Khlebnikov <khlebnikov@openvz.org> wrote:
> 
> > Andrew Morton wrote:
> >  >
> >  > (switched to email.  Please respond via emailed reply-to-all, not via the
> >  > bugzilla web interface).
> >  >
> >  > On Thu, 28 Jul 2011 12:41:03 GMT
> >  > bugzilla-daemon@bugzilla.kernel.org wrote:
> >  >
> >  >> https://bugzilla.kernel.org/show_bug.cgi?id=40262
> >  >
> >  > Two people are reporting this - there are some additional details in
> >  > bugzilla.
> >  >
> >  > We seem to be going around in circles here.
> >  >
> >  > I'll ask Rafael and Maciej to track this as a regression :(
> >  >
> > 
> > >>
> > >> issue occurs in new kernel 3.0.
> > >> does not occurs in 2.6.39.3/2.6.38.8
> > >>
> > 
> > I guess this can be caused by commit v2.6.39-6846-g246e87a "memcg: fix vmscan count in small memcgs"
> > (it also tweaked kswapd besides of memcg reclaimer)
> > it was fixed in v3.0-5361-g4508378 "memcg: fix get_scan_count() for small targets"
> > 
> > commit 4508378b9523e22a2a0175d8bf64d932fb10a67d
> > Author: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > Date:   Tue Jul 26 16:08:24 2011 -0700
> > 
> >      memcg: fix vmscan count in small memcgs
> > 
> >      Commit 246e87a93934 ("memcg: fix get_scan_count() for small targets")
> >      fixes the memcg/kswapd behavior against small targets and prevent vmscan
> >      priority too high.
> > 
> >      But the implementation is too naive and adds another problem to small
> >      memcg.  It always force scan to 32 pages of file/anon and doesn't handle
> >      swappiness and other rotate_info.  It makes vmscan to scan anon LRU
> >      regardless of swappiness and make reclaim bad.  This patch fixes it by
> >      adjusting scanning count with regard to swappiness at el.
> > 
> >      At a test "cat 1G file under 300M limit." (swappiness=20)
> >       before patch
> >              scanned_pages_by_limit 360919
> >              scanned_anon_pages_by_limit 180469
> >              scanned_file_pages_by_limit 180450
> >              rotated_pages_by_limit 31
> >              rotated_anon_pages_by_limit 25
> >              rotated_file_pages_by_limit 6
> >              freed_pages_by_limit 180458
> >              freed_anon_pages_by_limit 19
> >              freed_file_pages_by_limit 180439
> >              elapsed_ns_by_limit 429758872
> >       after patch
> >              scanned_pages_by_limit 180674
> >              scanned_anon_pages_by_limit 24
> >              scanned_file_pages_by_limit 180650
> >              rotated_pages_by_limit 35
> >              rotated_anon_pages_by_limit 24
> >              rotated_file_pages_by_limit 11
> >              freed_pages_by_limit 180634
> >              freed_anon_pages_by_limit 0
> >              freed_file_pages_by_limit 180634
> >              elapsed_ns_by_limit 367119089
> >              scanned_pages_by_system 0
> > 
> >      the numbers of scanning anon are decreased(as expected), and elapsed time
> >      reduced. By this patch, small memcgs will work better.
> >      (*) Because the amount of file-cache is much bigger than anon,
> >          recalaim_stat's rotate-scan counter make scanning files more.
> > 
> 
> Ah, yes. this patch may be able to fix the probelm...could you try ? 
> 
> Thanks,
> -Kame

I have applied your memcg-fix-vmscan-count-in-small-memcgs patch to the
new kernel v3.0.4. It works wonderfully, thank you a lot! I have tested
reading and copying large files and found that these operations do not
strain the memory of other applications anymore.

Thank you,
Steffen


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