linux-kernel - Re: [PATCH 06/10] vmscan: Split shrink

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Message-ID: <20100416142725.GE19264@csn.ul.ie>
Date:	Fri, 16 Apr 2010 15:27:25 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Chris Mason <chris.mason@...cle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 06/10] vmscan: Split shrink_zone to reduce stack usage

On Fri, Apr 16, 2010 at 02:23:08PM +1000, Dave Chinner wrote:
> On Thu, Apr 15, 2010 at 06:21:39PM +0100, Mel Gorman wrote:
> > shrink_zone() calculculates how many pages it needs to shrink from each
> > LRU list in a given pass. It uses a number of temporary variables to
> > work this out that then remain on the stack. This patch splits the
> > function so that some of the stack variables can be discarded.
> > 
> > Signed-off-by: Mel Gorman <mel@....ul.ie>
> > ---
> >  mm/vmscan.c |   29 +++++++++++++++++++----------
> >  1 files changed, 19 insertions(+), 10 deletions(-)
> > 
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 1ace7c6..a374879 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1595,19 +1595,14 @@ static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
> >  	return nr;
> >  }
> >  
> > -/*
> > - * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
> > - */
> > -static void shrink_zone(struct zone *zone, struct scan_control *sc)
> > +/* Calculate how many pages from each LRU list should be scanned */
> > +static void calc_scan_trybatch(struct zone *zone,
> > +				 struct scan_control *sc, unsigned long *nr)
> 
> Needs "noinline_for_stack" to stop the compiler re-inlining it.
> 

Agreed. I was using noinline where I spotted the compiler automatically
inlined but noinline_for_stack both handles future compiler changes and
is self-documenting. Thanks

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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