linux-kernel - Re: [PATCH 3/4] mm: move lazy free pages to inactive list

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Date:	Mon, 30 Mar 2015 22:28:47 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Shaohua Li <shli@...nel.org>, Yalin.Wang@...ymobile.com
Subject: Re: [PATCH 3/4] mm: move lazy free pages to inactive list

On Tue, 31 Mar 2015 13:45:25 +0900 Minchan Kim <minchan@...nel.org> wrote:
> > 
> > deactivate_page() doesn't look at or alter PageReferenced().  Should it?
> 
> Absolutely true. Thanks.
> Here it goes.
> 
> >From 2b2c92eb73a1cceac615b9abd4c0f5f0c3395ff5 Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@...nel.org>
> Date: Tue, 31 Mar 2015 13:38:46 +0900
> Subject: [PATCH] mm: lru_deactivate_fn should clear PG_referenced
> 
> deactivate_page aims for accelerate for reclaiming through
> moving pages from active list to inactive list so we should
> clear PG_referenced for the goal.
> 
> ...
>
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -800,6 +800,7 @@ static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
>  
>  		del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
>  		ClearPageActive(page);
> +		ClearPageReferenced(page);
>  		add_page_to_lru_list(page, lruvec, lru);
>  
>  		__count_vm_event(PGDEACTIVATE);

What if we have

	PageLRU(page) && !PageActive(page) && PageReferenced(page)

if we really want to "accelerate the reclaim of @page" then we should
clear PG_referenced there too.

(And what about page_referenced(page) :))
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