On Tue, 17 Aug 2010 19:36:02 -0700 (PDT)
David Rientjes <rientjes@xxxxxxxxxx> wrote:
> On Wed, 18 Aug 2010, KAMEZAWA Hiroyuki wrote:
>
> > > The oom killer's goal is to kill a memory-hogging task so that it may
> > > exit, free its memory, and allow the current context to allocate the
> > > memory that triggered it in the first place. Thus, killing a task is
> > > pointless if other threads sharing its mm cannot be killed because of its
> > > /proc/pid/oom_adj or /proc/pid/oom_score_adj value.
> > >
> > > This patch checks all user threads on the system to determine whether
> > > oom_badness(p) should return 0 for p, which means it should not be killed.
> > > If a thread shares p's mm and is unkillable, p is considered to be
> > > unkillable as well.
> > >
> > > Kthreads are not considered toward this rule since they only temporarily
> > > assume a task's mm via use_mm().
> > >
> > > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> >
> > Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> >
>
> Thanks!
>
> > Thank you. BTW, do you have good idea for speed-up ?
> > This code seems terribly slow when a system has many processes.
> >
>
> 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.
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)
Maybe no new lock is required and this not-accurate one will work enough.
Thanks,
-Kame
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