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The following patch has been helpful to find incorrect page accounting which results in problems ranging from unremovable cgroups to kernel warnings.

commit f212ad7cf9c73f8a7fa160e223dcb3f074441a72
Author: Daisuke Nishimura <nishimura.nec.co.jp>
Date:   Wed Mar 23 16:42:25 2011 -0700

    memcg: add memcg sanity checks at allocating and freeing pages
    
    Add checks at allocating or freeing a page whether the page is used (iow,
    charged) from the view point of memcg.
    
    This check may be useful in debugging a problem and we did similar checks
    before the commit 52d4b9ac(memcg: allocate all page_cgroup at boot).
    
    This patch adds some overheads at allocating or freeing memory, so it's
    enabled only when CONFIG_DEBUG_VM is enabled.
    
    Signed-off-by: Daisuke Nishimura <nishimura.nec.co.jp>
    Signed-off-by: Johannes Weiner <hannes>
    Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu.com>
    Cc: Balbir Singh <balbir.ibm.com>
    Cc: Minchan Kim <minchan.kim>
    Signed-off-by: Andrew Morton <akpm>
    Signed-off-by: Linus Torvalds <torvalds>

*** Bug 751855 has been marked as a duplicate of this bug. ***

This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.

Patch(es) available on kernel-2.6.32-241.el6

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2012-0862.html