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    SubjectRe: [RFC] oom-kill: give the dying task a higher priority
    On Fri, May 28, 2010 at 11:06:23PM +0900, Minchan Kim wrote:
    | On Fri, May 28, 2010 at 09:53:05AM -0300, Luis Claudio R. Goncalves wrote:
    | > On Fri, May 28, 2010 at 02:59:02PM +0900, KOSAKI Motohiro wrote:
    ...
    | > | As far as my observation, RT-function always have some syscall. because pure
    | > | calculation doesn't need deterministic guarantee. But _if_ you are really
    | > | using such priority design. I'm ok maximum NonRT priority instead maximum
    | > | RT priority too.
    | >
    | > I confess I failed to distinguish memcg OOM and system OOM and used "in
    | > case of OOM kill the selected task the faster you can" as the guideline.
    | > If the exit code path is short that shouldn't be a problem.
    | >
    | > Maybe the right way to go would be giving the dying task the biggest
    | > priority inside that memcg to be sure that it will be the next process from
    | > that memcg to be scheduled. Would that be reasonable?
    |
    | Hmm. I can't understand your point.
    | What do you mean failing distinguish memcg and system OOM?
    |
    | We already have been distinguish it by mem_cgroup_out_of_memory.
    | (but we have to enable CONFIG_CGROUP_MEM_RES_CTLR).
    | So task selected in select_bad_process is one out of memcg's tasks when
    | memcg have a memory pressure.

    The approach of giving the highest priority to the dying task makes sense
    in a system wide OOM situation. I though that would also be good for the
    memcg OOM case.

    After Balbir Singh's comment, I understand that in a memcg OOM the dying
    task should have a priority just above the priority of the main task of
    that memcg, in order to avoid interfering in the rest of the system.

    That is the point where I failed to distinguish between memcg and system OOM.

    Should I pursue that new idea of looking for the right priority inside the
    memcg or is it overkill? I really don't have a clear view of the impact of
    a memcg OOM on system performance - don't know if it is better to solve the
    issue sooner (highest RT priority) or leave it to be solved later (highest
    prio on the memcg). I have the impression the general case points to the
    simpler solution.

    Luis
    --
    [ Luis Claudio R. Goncalves Bass - Gospel - RT ]
    [ Fingerprint: 4FDD B8C4 3C59 34BD 8BE9 2696 7203 D980 A448 C8F8 ]



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