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

KOSAKI Motohiro
2011-05-24T01:56:07Z

>>> 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.