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Groups > linux.kernel > #1408935
| From | Vladimir Davydov <vdavydov@virtuozzo.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj |
| Date | 2016-05-30 11:30 +0200 |
| Message-ID | <rErGh-2in-15@gated-at.bofh.it> (permalink) |
| References | <rD2TD-6uy-5@gated-at.bofh.it> <rD2TE-6uy-27@gated-at.bofh.it> <rDnY6-2JR-17@gated-at.bofh.it> <rDsEq-5Ht-27@gated-at.bofh.it> <rEpuP-YG-47@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Mon, May 30, 2016 at 09:07:05AM +0200, Michal Hocko wrote:
> On Fri 27-05-16 19:18:21, Vladimir Davydov wrote:
> > On Fri, May 27, 2016 at 01:18:03PM +0200, Michal Hocko wrote:
> > ...
> > > @@ -1087,7 +1105,25 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
> > > unlock_task_sighand(task, &flags);
> > > err_put_task:
> > > put_task_struct(task);
> > > +
> > > + if (mm) {
> > > + struct task_struct *p;
> > > +
> > > + rcu_read_lock();
> > > + for_each_process(p) {
> > > + task_lock(p);
> > > + if (!p->vfork_done && process_shares_mm(p, mm)) {
> > > + p->signal->oom_score_adj = oom_adj;
> > > + if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE))
> > > + p->signal->oom_score_adj_min = (short)oom_adj;
> > > + }
> > > + task_unlock(p);
> >
> > I.e. you write to /proc/pid1/oom_score_adj and get
> > /proc/pid2/oom_score_adj updated if pid1 and pid2 share mm?
> > IMO that looks unexpected from userspace pov.
>
> How much different it is from threads in the same thread group?
> Processes sharing the mm without signals is a rather weird threading
> model isn't it?
I think so too. I wouldn't be surprised if it turned out that nobody had
ever used it. But may be there's someone out there who does.
> Currently we just lie to users about their oom_score_adj
> in this weird corner case.
Hmm, looks like a bug, but nobody has ever complained about it.
> The only exception was OOM_SCORE_ADJ_MIN
> where we really didn't kill the task but all other values are simply
> ignored in practice.
>
> > May be, we'd better add mm->oom_score_adj and set it to the min
> > signal->oom_score_adj over all processes sharing it? This would
> > require iterating over all processes every time oom_score_adj gets
> > updated, but that's a slow path.
>
> Not sure I understand. So you would prefer that mm->oom_score_adj might
> disagree with p->signal->oom_score_adj?
No, I wouldn't. I'd rather agree that oom_score_adj should be per mm,
because we choose the victim basing solely on mm stats.
What I mean is we don't touch p->signal->oom_score_adj of other tasks
sharing mm, but instead store minimal oom_score_adj over all tasks
sharing mm in the mm_struct whenever a task's oom_score_adj is modified.
And use mm->oom_score_adj instead of signal->oom_score_adj in oom killer
code. This would save us from any accusations of user API modifications
and it would also make the oom code a bit easier to follow IMHO.
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[PATCH 0/5] Handle oom bypass more gracefully Michal Hocko <mhocko@kernel.org> - 2016-05-26 14:50 +0200
[PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko <mhocko@kernel.org> - 2016-05-26 14:50 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko <mhocko@kernel.org> - 2016-05-27 13:20 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Vladimir Davydov <vdavydov@virtuozzo.com> - 2016-05-27 18:20 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko <mhocko@kernel.org> - 2016-05-30 09:10 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Vladimir Davydov <vdavydov@virtuozzo.com> - 2016-05-30 11:30 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko <mhocko@kernel.org> - 2016-05-30 11:50 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Vladimir Davydov <vdavydov@virtuozzo.com> - 2016-05-30 12:50 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko <mhocko@kernel.org> - 2016-05-30 13:20 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Vladimir Davydov <vdavydov@virtuozzo.com> - 2016-05-30 14:30 +0200
Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko <mhocko@kernel.org> - 2016-05-30 14:30 +0200
[PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm Michal Hocko <mhocko@kernel.org> - 2016-05-26 14:50 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-26 16:40 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm Michal Hocko <mhocko@kernel.org> - 2016-05-26 17:00 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are noexternal tasks sharing mm Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-26 17:30 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are noexternal tasks sharing mm Michal Hocko <mhocko@kernel.org> - 2016-05-26 17:40 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-05-26 18:20 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm Michal Hocko <mhocko@kernel.org> - 2016-05-27 08:50 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm Michal Hocko <mhocko@kernel.org> - 2016-05-27 09:20 +0200
Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm Michal Hocko <mhocko@kernel.org> - 2016-05-27 10:10 +0200
[PATCH 2/6] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko <mhocko@kernel.org> - 2016-05-26 14:50 +0200
Re: [PATCH 0/5] Handle oom bypass more gracefully Michal Hocko <mhocko@kernel.org> - 2016-05-27 18:10 +0200
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