linux-kernel - Re: Page scan keeps touching kernel text pages

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Message-ID: <20080225185319.GA14699@lazybastard.org>
Date:	Mon, 25 Feb 2008 19:53:20 +0100
From:	Jörn Engel <joern@...fs.org>
To:	Dave Hansen <haveblue@...ibm.com>
Cc:	Andy Whitcroft <apw@...dowen.org>,
	Jörn Engel <joern@...fs.org>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: Page scan keeps touching kernel text pages

On Mon, 25 February 2008 09:48:22 -0800, Dave Hansen wrote:
> On Mon, 2008-02-25 at 15:07 +0000, Andy Whitcroft wrote:
> > shrink_page_list() would be expected to be passed pages pulled from
> > the active or inactive lists via isolate_lru_pages()?  I would not have
> > expected to find the kernel text on the LRU and therefore not expect to
> > see it passed to shrink_page_list()?
> 
> It may have been kernel text at one time, but what about __init
> functions?  Don't we free that section back to the normal allocator
> after init time?  Those can end up on the LRU.

Pages below 0x2ba should be non-init in my test kernel:
c02ba000 T __init_begin
...
c02d5000 B __init_end

scanning zone DMA
page      3fa        3 00000000 628
page      2bf        2 00000000 628
page       97        3 00000000 628
page       98        2 00000000 628

So __init explains one page of this minimal sample, but not the other
three.

Jörn

-- 
Never argue with idiots - first they drag you down to their level,
then they beat you with experience.
-- unknown
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