linux-kernel - Re: [PATCH 3/3] vmscan: merge duplicate code in shrink_active

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Message-ID: <20090516134718.GA15263@localhost>
Date:	Sat, 16 May 2009 21:47:18 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"peterz@...radead.org" <peterz@...radead.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>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>
Subject: Re: [PATCH 3/3] vmscan: merge duplicate code in
	shrink_active_list()

On Sat, May 16, 2009 at 09:39:50PM +0800, Johannes Weiner wrote:
> On Sat, May 16, 2009 at 05:00:08PM +0800, Wu Fengguang wrote:
> > The "move pages to active list" and "move pages to inactive list"
> > code blocks are mostly identical and can be served by a function.
> > 
> > Thanks to Andrew Morton for pointing this out.
> > 
> > Note that buffer_heads_over_limit check will also be carried out
> > for re-activated pages, which is slightly different from pre-2.6.28
> > kernels. Also, Rik's "vmscan: evict use-once pages first" patch
> > could totally stop scans of active list when memory pressure is low.
> > So the net effect could be, the number of buffer heads is now more
> > likely to grow large.
> 
> I don't think that this could be harmful.  We just preserve the buffer
> mappings of what we consider the working set and with low memory
> pressure, as you say, this set is not big.
> 
> As to stripping of reactivated pages: the only pages we re-activate
> for now are those VM_EXEC mapped ones.  Since we don't expect IO from
> or to these pages, removing the buffer mappings in case they grow too
> large should be okay, I guess.

Agreed - and good analyzes, thanks!

Fengguang

> > CC: Rik van Riel <riel@...hat.com>
> > Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> 
> Reviewed-by: Johannes Weiner <hannes@...xchg.org>
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