linux-kernel - Re: [PATCH -mm] vmscan: report vm_flags in page

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Date:	Tue, 12 May 2009 15:44:13 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	"riel@...hat.com" <riel@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tytso@....edu" <tytso@....edu>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"elladan@...imo.com" <elladan@...imo.com>,
	"npiggin@...e.de" <npiggin@...e.de>,
	"cl@...ux-foundation.org" <cl@...ux-foundation.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>
Subject: Re: [PATCH -mm] vmscan: report vm_flags in page_referenced()

On Tue, 12 May 2009 08:23:09 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> On Tue, 2009-05-12 at 10:51 +0800, Wu Fengguang wrote:
> > @@ -406,6 +408,7 @@ static int page_referenced_anon(struct p
> >                 if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
> >                         continue;
> >                 referenced += page_referenced_one(page, vma, &mapcount);
> > +               *vm_flags |= vma->vm_flags;
> >                 if (!mapcount)
> >                         break;
> >         }
> 
> Shouldn't that read:
> 
>   if (page_referenced_on(page, vma, &mapcount)) {
>     referenced++;
>     *vm_flags |= vma->vm_flags;
>   }
> 
> So that we only add the vma-flags of those vmas that actually have a
> young bit set?
> 
> In which case it'd be more at home in page_referenced_one():
> 
> @@ -381,6 +381,8 @@ out_unmap:
>  	(*mapcount)--;
>  	pte_unmap_unlock(pte, ptl);
>  out:
> +	if (referenced)
> +		*vm_flags |= vma->vm_flags;
>  	return referenced;
>  }

Good. I am ACK for peter's suggestion.
It can prevent setting vm_flag for worng vma which don't have the page.

-- 
Kinds Regards
Minchan Kim
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