Messages in this thread | | | Date | Thu, 13 Dec 2007 09:23:38 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 0/6] Use two zonelists per node instead of multiple zonelists v11r2 |
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On Wed, 12 Dec 2007 16:32:51 -0500 Lee Schermerhorn <Lee.Schermerhorn@hp.com> wrote:
> Just this afternoon, I hit a null pointer deref in > __mem_cgroup_remove_list() [called from mem_cgroup_uncharge() if I can > trust the stack trace] attempting to unmap a page for migration. I'm > just starting to investigate this. > > I'll replace the series I have [~V10] with V11r2 and continue testing in > anticipation of the day that we can get this into -mm. > Hi, Lee-san.
Could you know what is the caller of page migration ? system call ? hot removal ? or some new thing ?
Note: 2.6.24-rc4-mm1's cgroup/migration logic.
In 2.6.24-rc4-mm1, in page migration, mem_cgroup_prepare_migration() increments page_cgroup's refcnt before calling try_to_unmap(). This extra refcnt guarantees the page_cgroup's refcnt will not drop to 0 in sequence of unmap_and_move() -> try_to_unmap() -> page_remove_rmap() -> mem_cgroup_unchage().
Thanks, -Kame
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