linux-kernel - Re: mapped pagecache pages vs unmapped pages

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Date:	Tue, 10 Apr 2012 10:25:08 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Rik van Riel <riel@...hat.com>, hannes@...xchg.org
CC:	Alexey Ivanov <rbtz@...dex-team.ru>,
	"gnehzuil.lzheng@...il.com" <gnehzuil.lzheng@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, yinghan@...gle.com
Subject: Re: mapped pagecache pages vs unmapped pages

2012-04-10 오전 9:49, Rik van Riel 쓴 글:

> On 04/09/2012 08:31 PM, Minchan Kim wrote:
>> 2012-04-10 오전 8:50, Alexey Ivanov 쓴 글:
>>
>>> Did you consider making this ratio tunable, at least manually(i.e.
>>> via sysctl)?
>>> I suppose we are not the only ones with almost-whole-ram-mmaped
>>> workload.
>>
>> Personally, I think it's not good approach.
>> It depends on kernel's internal implemenatation which would be changed
>> in future as we chagend it at 2.6.28.
> 
> I also believe that a tunable for this is not going to be
> a very workable approach, for the simple reason that changing
> the value does not make a predictable change in the effectiveness
> of working set detection or protection.
> 
>> In my opinion, kernel just should do best effort to keep active working
>> set except some critical pages which are code pages.
> 
> Johannes has some experimental code to measure refaults, and
> calculate their distance in a multi-zone, multi-cgroup environment.
> 
> That would allow us to predictably place things in the working set
> as required.
> 


Hannes, it can help many people if you post your code. ;)


-- 
Kind regards,
Minchan Kim
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