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    SubjectRe: [RFC] oom-kill: give the dying task a higher priority
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    > * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2010-05-28 13:46:53]:
    >
    > > > * Luis Claudio R. Goncalves <lclaudio@uudg.org> [2010-05-28 00:51:47]:
    > > >
    > > > > @@ -382,6 +382,8 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
    > > > > */
    > > > > static void __oom_kill_task(struct task_struct *p, int verbose)
    > > > > {
    > > > > + struct sched_param param;
    > > > > +
    > > > > if (is_global_init(p)) {
    > > > > WARN_ON(1);
    > > > > printk(KERN_WARNING "tried to kill init!\n");
    > > > > @@ -413,8 +415,9 @@ static void __oom_kill_task(struct task_struct *p, int verbose)
    > > > > */
    > > > > p->rt.time_slice = HZ;
    > > > > set_tsk_thread_flag(p, TIF_MEMDIE);
    > > > > -
    > > > > force_sig(SIGKILL, p);
    > > > > + param.sched_priority = MAX_RT_PRIO-1;
    > > > > + sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
    > > > > }
    > > > >
    > > >
    > > > I would like to understand the visible benefits of this patch. Have
    > > > you seen an OOM kill tasked really get bogged down. Should this task
    > > > really be competing with other important tasks for run time?
    > >
    > > What you mean important? Until OOM victim task exit completely, the system have no memory.
    > > all of important task can't do anything.
    > >
    > > In almost kernel subsystems, automatically priority boost is really bad idea because
    > > it may break RT task's deterministic behavior. but OOM is one of exception. The deterministic
    > > was alread broken by memory starvation.
    > >
    >
    > I am still not convinced, specially if we are running under mem
    > cgroup. Even setting SCHED_FIFO does not help, you could have other
    > things like cpusets that might restrict the CPUs you can run on, or
    > any other policy and we could end up contending anyway with other
    > SCHED_FIFO tasks.

    Ah, right you are. I had missed mem-cgroup.
    But I think memcgroup also don't need following two boost. Can we get rid of it?

    p->rt.time_slice = HZ;
    set_tsk_thread_flag(p, TIF_MEMDIE);


    I mean we need distinguish global oom and memcg oom, perhapls.


    > > That's the reason I acked it.
    >
    > If we could show faster recovery from OOM or anything else, I would be
    > more convinced.








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