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Description of problem: src nr_shmem underflow during migration and another zone has it boosted by mistake Version-Release number of selected component (if applicable): How reproducible: easy Steps to Reproduce: 1. allocate order > 0 pages with THP, hugetlbfs or jumbo frames triggering a lot of compaction that in turn will run a lot of migrate_pages (the bug is in the migration code) and push the system into swap while the hugepage allocations are running (swap must be present as the bug triggers only with lots of swapcache allocated) 2. run egrep 'Node|nr_shmem' /proc/zoneinfo 3. Actual results: nr_shmem should be correct (with CONFIG_SMP=y we'll only see some zone increasing nr_shmem too much, we won't see the actual overflow because on SMP the nr_shmem will be returned 0 even if it's negative if casted to "signed long", with CONFIG_SMP=n a negative nr_shmem value should be visible for some zone) Expected results: the nr_shmem statistics should be accurate for each zone Additional info: This seems only an aesthetical problem, not resulting in any runtime error. I'm not aware of any application reading nr_shmem from /proc/zoneinfo. nr_shmem in /proc/vmstat and /proc/meminfo should not be affected, only the _per-zone_ statistics are affected. So it's a minor 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-2.6.32-169.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-2011-1530.html