linux-kernel - Re: Over-eager swapping

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Message-ID: <20100803042835.GA17377@localhost>
Date:	Tue, 3 Aug 2010 12:28:35 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Chris Webb <chris@...chsys.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: Over-eager swapping

On Tue, Aug 03, 2010 at 12:09:18PM +0800, Minchan Kim wrote:
> On Tue, Aug 3, 2010 at 12:31 PM, Chris Webb <chris@...chsys.com> wrote:
> > Minchan Kim <minchan.kim@...il.com> writes:
> >
> >> Another possibility is _zone_reclaim_ in NUMA.
> >> Your working set has many anonymous page.
> >>
> >> The zone_reclaim set priority to ZONE_RECLAIM_PRIORITY.
> >> It can make reclaim mode to lumpy so it can page out anon pages.
> >>
> >> Could you show me /proc/sys/vm/[zone_reclaim_mode/min_unmapped_ratio] ?
> >
> > Sure, no problem. On the machine with the /proc/meminfo I showed earlier,
> > these are
> >
> >  # cat /proc/sys/vm/zone_reclaim_mode
> >  0
> >  # cat /proc/sys/vm/min_unmapped_ratio
> >  1
> 
> if zone_reclaim_mode is zero, it doesn't swap out anon_pages.

If there are lots of order-1 or higher allocations, anonymous pages
will be randomly evicted, regardless of their LRU ages. This is
probably another factor why the users claim. Are there easy ways to
confirm this other than patching the kernel?

Chris, what's in your /proc/slabinfo?

Thanks,
Fengguang
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