Re: [PATCH mmotm] vmscan: handle may_swap more strictly (Re: [PATCH mmotm] vmscan: fix may_swap handling for memcg)

[Minchan Kim]

On Tue, Jun 9, 2009 at 5:24 PM, KOSAKI
Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>> On Tue, Jun 9, 2009 at 4:58 PM, KOSAKI
>> Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>> >> Hi, KOSAKI.
>> >>
>> >> As you know, this problem caused by if condition(priority) in shrink_zone.
>> >> Let me have a question.
>> >>
>> >> Why do we have to prevent scan value calculation when the priority is zero ?
>> >> As I know, before split-lru, we didn't do it.
>> >>
>> >> Is there any specific issue in case of the priority is zero ?
>> >
>> > Yes.
>> >
>> > example:
>> >
>> > get_scan_ratio() return anon:80%, file=20%. and the system have
>> > 10000 anon pages and 10000 file pages.
>> >
>> > shrink_zone() picked up 8000 anon pages and 2000 file pages.
>> > it mean 8000 file pages aren't scanned at all.
>> >
>> > Oops, it can makes OOM-killer although system have droppable file cache.
>> >
>> Hmm..Can that problem be happen in real system ?
>> The file ratio is big means that file lru list scanning is so big but
>> rotate is small.
>> It means file lru have few reclaimable page.
>>
>> Isn't it ? I am confusing.
>> Could you elaborate, please if you don't mind ?
>
> hm, ok, my example was wrong.
> I intention is, if there are droppable file-back pages (althout only 1 page),
> OOM-killer shouldn't occuer.
>
> many or few is unrelated.
>

I am not sure that is effective.
Have you ever met this problem in real situation ?

BTW, I have to dive into code. :)
Thanks for spending valuable time for commenting

-- 
Kinds regards,
Minchan Kim
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