Re: [PATCH 4/5] oom: don't kill random process

[KOSAKI Motohiro]

> > > This is unnecessary and just makes the oom killer egregiously long.  We
> > > are already diagnosing problems here at Google where the oom killer holds
> > > tasklist_lock on the readside for far too long, causing other cpus waiting
> > > for a write_lock_irq(&tasklist_lock) to encounter issues when irqs are
> > > disabled and it is spinning.  A second tasklist scan is simply a
> > > non-starter.
> > >
> > >    [ This is also one of the reasons why we needed to introduce
> > >      mm->oom_disable_count to prevent a second, expensive tasklist scan. ]
> >
> > You misunderstand the code. Both select_bad_process() and oom_kill_process()
> > are under tasklist_lock(). IOW, no change lock holding time.
>
> A second iteration through the tasklist in select_bad_process() will
> extend the time that tasklist_lock is held, which is what your patch does.

It never happen usual case. Plz think when happen all process score = 1.

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