linux-kernel - Re: [RFC 1/2] deactive invalidated pages

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Message-ID: <AANLkTin62R1=2P+Sh0YKJ3=KAa6RfLQLKJcn2VEtoZfG@mail.gmail.com>
Date:	Tue, 23 Nov 2010 14:23:33 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...nel.dk>
Subject: Re: [RFC 1/2] deactive invalidated pages

On Tue, Nov 23, 2010 at 2:01 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Tue, 23 Nov 2010 13:52:05 +0900 Minchan Kim <minchan.kim@...il.com> wrote:
>
>> >> +/*
>> >> + * Function used to forecefully demote a page to the head of the inactive
>> >> + * list.
>> >> + */
>> >
>> > This comment is wrong? __The page gets moved to the _tail_ of the
>> > inactive list?
>>
>> No. I add it in _head_ of the inactive list intentionally.
>> Why I don't add it to _tail_ is that I don't want to be aggressive.
>> The page might be real working set. So I want to give a chance to
>> activate it again.
>
> Well..  why?  The user just tried to toss the page away altogether.  If
> the kernel wasn't able to do that immediately, the best it can do is to
> toss the page away asap?
>
>> If it's not working set, it can be reclaimed easily and it can prevent
>> active page demotion since inactive list size would be big enough for
>> not calling shrink_active_list.
>
> What is "working set"?  Mapped and unmapped pagecache, or are you
> referring solely to mapped pagecache?

I mean it's mapped by other processes.

>
> If it's mapped pagecache then the user was being a bit silly (or didn't
> know that some other process had mapped the file).  In which case we
> need to decide what to do - leave the page alone, deactivate it, or
> half-deactivate it as this patch does.


What I want is the half-deactivate.

Okay. We will use the result of invalidate_inode_page.
If fail happens by page_mapped, we can do half-deactivate.
But if fail happens by dirty(ex, writeback), we can add it to tail.
Does it make sense?



-- 
Kind regards,
Minchan Kim
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