linux-kernel - Re: [rfc 3/3] mm: vmscan: revert file list boost on lru addition

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Message-ID: <20111110161244.GN3153@redhat.com>
Date:	Thu, 10 Nov 2011 17:12:44 +0100
From:	Johannes Weiner <jweiner@...hat.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Konstantin Khlebnikov <khlebnikov@...allels.com>,
	Pekka Enberg <penberg@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Minchan Kim <minchan.kim@...il.com>,
	Gene Heskett <gene.heskett@...il.com>
Subject: Re: [rfc 3/3] mm: vmscan: revert file list boost on lru addition

On Mon, Nov 07, 2011 at 11:45:20AM +0900, KAMEZAWA Hiroyuki wrote:
> On Wed, 2 Nov 2011 17:32:47 +0100
> Johannes Weiner <jweiner@...hat.com> wrote:
> 
> > The idea in 9ff473b 'vmscan: evict streaming IO first' was to steer
> > reclaim focus onto file pages with every new file page that hits the
> > lru list, so that an influx of used-once file pages does not lead to
> > swapping of anonymous pages.
> > 
> > The problem is that nobody is fixing up the balance if the pages in
> > fact become part of the resident set.
> > 
> > Anonymous page creation is neutral to the inter-lru balance, so even a
> > comparably tiny number of heavily used file pages tip the balance in
> > favor of the file list.
> > 
> > In addition, there is no refault detection, and every refault will
> > bias the balance even more.  A thrashing file working set will be
> > mistaken for a very lucrative source of reclaimable pages.
> > 
> > As anonymous pages are no longer swapped above a certain priority
> > level, this mechanism is no longer needed.  Used-once file pages
> > should get reclaimed before the VM even considers swapping.
> > 
> > Signed-off-by: Johannes Weiner <jweiner@...hat.com>
> 
> Do you have some results ?

Not yet, sorry, I had to drop it all and do something else.

This change relies on the VM having a different mechanism to go for
one-shot file cache first, so I need to address Kosaki-san's concerns
about 1/3 before pursuing this patch.
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