linux-kernel - Re: [PATCH 1/2] vmscan: promote shared file mapped pages

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Date:	Tue, 9 Aug 2011 08:51:30 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	<linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 1/2] vmscan: promote shared file mapped pages

On Mon, 8 Aug 2011 15:06:58 +0400
Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:

> Commit v2.6.33-5448-g6457474 (vmscan: detect mapped file pages used only once)
> greatly decreases lifetime of single-used mapped file pages.
> Unfortunately it also decreases life time of all shared mapped file pages.
> Because after commit v2.6.28-6130-gbf3f3bc (mm: don't mark_page_accessed in fault path)
> page-fault handler does not mark page active or even referenced.
> 
> Thus page_check_references() activates file page only if it was used twice while
> it stays in inactive list, meanwhile it activates anon pages after first access.
> Inactive list can be small enough, this way reclaimer can accidentally
> throw away any widely used page if it wasn't used twice in short period.
> 
> After this patch page_check_references() also activate file mapped page at first
> inactive list scan if this page is already used multiple times via several ptes.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>

As other guys pointed out, it's better to show performance score change by
this patch in changelog.

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

> ---
>  mm/vmscan.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 47403c9..3cd766d 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -724,7 +724,7 @@ static enum page_references page_check_references(struct page *page,
>  		 */
>  		SetPageReferenced(page);
>  
> -		if (referenced_page)
> +		if (referenced_page || referenced_ptes > 1)
>  			return PAGEREF_ACTIVATE;
>  
>  		return PAGEREF_KEEP;
> 
> 

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