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    SubjectRe: [RFC PATCH] memcg: oom: fix totalpages calculation for swappiness==0
    On Wed 10-10-12 13:50:21, David Rientjes wrote:
    > On Wed, 10 Oct 2012, Michal Hocko wrote:
    >
    > > Hi,
    > > I am sending the patch below as an RFC because I am not entirely happy
    > > about myself and maybe somebody can come up with a different approach
    > > which would be less hackish.
    >
    > I don't see this as hackish,

    I didn't like how swappiness spreads outside of the LRU scanning code...

    > if memory.swappiness limits access to swap then this shouldn't be
    > factored into the calculation, and that's what your patch fixes.
    >
    > The reason why the process with the largest rss isn't killed in this case
    > is because all processes have CAP_SYS_ADMIN so they get a 3% bonus;

    OK I should have mentioned that I have tested it as root which makes a
    big difference with the current upstream as totalpages are considered
    only if adj!=0.
    I have originally seen the problem in 3.0 kernel (with fe35004f applied)
    where the calculation is different (missing a7f638f9) and we always
    consider total_pages there so it doesn't depend on root or oom_score_adj.

    > when factoring swap into the calculation and subtracting 3% from
    > the score in oom_badness(), they all end up having an internal
    > score of 1 so they are all considered equal. It appears like the
    > cgroup_iter_next() iteration for memcg ooms does this in reverse
    > order, which is actually helpful so it will select the task that is
    > newer.
    >
    > The only suggestion I have to make is specify this is for
    > memory.swappiness in the patch title, otherwise:

    OK. I will also update the changelog to mention oom_score_adj and
    CAP_SYS_ADMIN, mark the patch for stable and repost it.

    > Acked-by: David Rientjes <rientjes@google.com>

    Thanks
    --
    Michal Hocko
    SUSE Labs


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