Am Montag, den 29.08.2011, 09:01 +0900 schrieb KAMEZAWA Hiroyuki: 

On Sun, 28 Aug 2011 15:13:35 +0400
Konstantin Khlebnikov [off-list ref] wrote:

quoted

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 :(
 >

quoted

quoted

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 [off-list ref]
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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