linux-kernel - Re: [patch 1/3] vmscan: factor out page reference checks

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Date:	Tue, 23 Feb 2010 23:44:14 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/3] vmscan: factor out page reference checks

On Tue, 2010-02-23 at 15:21 +0100, Johannes Weiner wrote:
> Hello Minchan,
> 
> On Tue, Feb 23, 2010 at 10:38:23PM +0900, Minchan Kim wrote:

<snip>

> > >  
> > >  		if (PageDirty(page)) {
> > > -			if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
> > > +			if (references == PAGEREF_RECLAIM_CLEAN)
> > 
> > How equal PAGEREF_RECLAIM_CLEAN and sc->order <= PAGE_ALLOC_COSTLY_ORDER
> > && referenced by semantic?
> 
> It is encoded in page_check_references().  When
> 	sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced
> it returns PAGEREF_RECLAIM_CLEAN.
> 
> So
> 
> 	- PageDirty() && order < COSTLY && referenced
> 	+ PageDirty() && references == PAGEREF_RECLAIM_CLEAN
> 
> is an equivalent transformation.  Does this answer your question?

Hmm. I knew it. My point was PAGEREF_RECLAIM_CLEAN seems to be a little
awkward. I thought PAGEREF_RECLAIM_CLEAN means if the page was clean, it
can be reclaimed.

I think it would be better to rename it with represent "Although it's
referenced page recently, we can reclaim it if VM try to reclaim high
order page".


> 
> 	Hannes


-- 
Kind regards,
Minchan Kim


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