linux-kernel - Re: [PATCH] vmscan: prevent background aging of anon page in no swap system

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Message-ID: <AANLkTik=6kRdz0LJnRRhddW_Lp8osis-4Y7EGc4u5x0z@mail.gmail.com>
Date:	Tue, 31 Aug 2010 12:46:53 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Ying Han <yinghan@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] vmscan: prevent background aging of anon page in no swap system

On Tue, Aug 31, 2010 at 11:30 AM, Rik van Riel <riel@...hat.com> wrote:
> On 08/30/2010 09:23 PM, Minchan Kim wrote:
>
>> Ying's one and mine both has a same effect.
>> Only difference happens swap is full. My version maintains old
>> behavior but Ying's one changes the behavior. I admit swap full is
>> rare event but I hoped not changed old behavior if we doesn't find any
>> problem.
>> If kswapd does aging when swap full happens, is it a problem?
>
> It may be a good thing, since swap will often be freed again
> (when something is swapped in, or exits).
>
> Having some more anonymous pages sit on the inactive list
> gives them a chance to get used again, potentially giving
> us a better chance of preserving the working set when swap
> is full or near full a lot of the time.

Do you mean we would be better to do background aging when swap is full?
I wanted it. So I used total_swap_pages to protect working set when
swap is full.
But Ying and KOSAKI's don't like it since it makes code inconsistent
or not simply.
And I agree it's rare event as KOSAKI mentioned.

Hmm... What do you think about it?

If you don't mind, I will resend latest version(use nr_swap_page usage
and compile out inactive_anon_is_low in case of !CONFIG_SWAP).


-- 
Kind regards,
Minchan Kim
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