linux-kernel - Re: [RFC] respect the referenced bit of KVM guest pages?

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Date:	Fri, 21 Aug 2009 20:17:51 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Jeff Dike <jdike@...toit.com>, Avi Kivity <avi@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"Yu, Wilfred" <wilfred.yu@...el.com>,
	"Kleen, Andi" <andi.kleen@...el.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC] respect the referenced bit of KVM guest pages?

>> Hmm, I think
>>
>> 1. Anyway, we need turn on PG_mlock.
>
> I add my patch again to explain.
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index ed63894..283266c 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -358,6 +358,7 @@ static int page_referenced_one(struct page *page,
>         */
>        if (vma->vm_flags & VM_LOCKED) {
>                *mapcount = 1;  /* break early from loop */
> +               *vm_flags |= VM_LOCKED;
>                goto out_unmap;
>        }
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d224b28..d156e1d 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -632,7 +632,8 @@ static unsigned long shrink_page_list(struct
> list_head *page_list,
>                                                sc->mem_cgroup, &vm_flags);
>                /* In active use or really unfreeable?  Activate it. */
>                if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
> -                                       referenced && page_mapping_inuse(page))
> +                                       referenced && page_mapping_inuse(page)
> +                                       && !(vm_flags & VM_LOCKED))
>                        goto activate_locked;
>
> By this check, the page can be reached at try_to_unmap after
> page_referenced in shrink_page_list. At that time PG_mlocked will be
> set.

You are right.
Please add my Reviewed-by sign to your patch.

Thanks.
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