On Wed, 18 Aug 2010, KAMEZAWA Hiroyuki wrote:
> > I was thinking about adding an "unsinged long oom_kill_disable_count" to
> > struct mm_struct that would atomically increment anytime a task attached
> > to it had a signal->oom_score_adj of OOM_SCORE_ADJ_MIN.
> >
> > The proc handler when changing /proc/pid/oom_score_adj would inc or dec
> > the counter depending on the new value, and exit_mm() would dec the
> > counter if current->signal->oom_score_adj is OOM_SCORE_ADJ_MIN.
> >
> > What do you think?
> >
>
> Hmm. I want to make hooks to "exit" small.
>
Is it worth adding
if (unlikely(current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN))
atomic_dec(¤t->mm->oom_disable_count);
to exit_mm() under task_lock() to avoid the O(n^2) select_bad_process() on
oom? Or do you think that's too expensive?
> One idea is.
>
> add a new member
> mm->unkiilable_by_oom_jiffies.
>
> And add
> > +static bool is_mm_unfreeable(struct mm_struct *mm)
> > +{
> > + struct task_struct *p;
> > +
> if (mm->unkillable_by_oom_jiffies < jiffies)
> return true;
>
> > + for_each_process(p)
> > + if (p->mm == mm && !(p->flags & PF_KTHREAD) &&
> > + p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
>
> mm->unkillable_by_oom_jiffies = jiffies + HZ;
>
> > + return true;
> > + return false;
> > +}+static bool is_mm_unfreeable(struct mm_struct *mm)
>
This probably isn't fast enough for the common case, which is when no
tasks for "mm" have an oom_score_adj of OOM_SCORE_ADJ_MIN, since it still
iterates through every task.
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