linux-kernel - Re: [PATCH] mm/vmscan.c: avoid recording the original scan targets in shrink

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Message-ID: <20140610002410.GB8171@bbox>
Date:	Tue, 10 Jun 2014 09:24:10 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Chen Yucong <slaoub@...il.com>
Cc:	mgorman@...e.de, mhocko@...e.cz, hannes@...xchg.org,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmscan.c: avoid recording the original scan targets
 in shrink_lruvec()

On Tue, Jun 10, 2014 at 08:10:51AM +0800, Chen Yucong wrote:
> On Tue, 2014-06-10 at 08:24 +0900, Minchan Kim wrote:
> > Hello,
> > 
> > On Mon, Jun 09, 2014 at 09:27:16PM +0800, Chen Yucong wrote:
> > > Via https://lkml.org/lkml/2013/4/10/334 , we can find that recording the
> > > original scan targets introduces extra 40 bytes on the stack. This patch
> > > is able to avoid this situation and the call to memcpy(). At the same time,
> > > it does not change the relative design idea.
> > > 
> > > ratio = original_nr_file / original_nr_anon;
> > > 
> > > If (nr_file > nr_anon), then ratio = (nr_file - x) / nr_anon.
> > >  x = nr_file - ratio * nr_anon;
> > > 
> > > if (nr_file <= nr_anon), then ratio = nr_file / (nr_anon - x).
> > >  x = nr_anon - nr_file / ratio;
> > 
> > Nice cleanup!
> > 
> > Below one nitpick.
> > 
> 
> > 
> > If both nr_file and nr_anon are zero, then the nr_anon could be zero
> > if HugePage are reclaimed so that it could pass the below check
> > 
> >         if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
> > 
> > 
> The Mel Gorman's patch has already handled this situation you're
> describing. It's called:
>  
> mm: vmscan: use proportional scanning during direct reclaim and full
> scan at DEF_PRIORITY

It seems I was far away from vmscan.c for a while.
Thanks for the pointing out. So,

Acked-by: Minchan Kim <minchan@...nel.org>

-- 
Kind regards,
Minchan Kim
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