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Date: Thu, 29 Jan 2015 10:24:07 +0900
From: Minchan Kim <minchan@kernel.org>
Subject: Re: OOM at low page cache?
Message-ID: <20150129012356.GA9672@blaptop>
References: <54C2C89C.8080002@gmail.com>
 <54C77086.7090505@suse.cz>
 <20150128062609.GA4706@blaptop>
 <54C8EF16.5080701@gmail.com>
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To: John Moser <john.r.moser@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>, linux-kernel@vger.kernel.org, "linux-mm@kvack.org" <linux-mm@kvack.org>, Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Christoph Lameter <cl@linux-foundation.org>

Hello,

On Wed, Jan 28, 2015 at 09:15:50AM -0500, John Moser wrote:
> On 01/28/2015 01:26 AM, Minchan Kim wrote:
> > Hello,
> >
> > On Tue, Jan 27, 2015 at 12:03:34PM +0100, Vlastimil Babka wrote:
> >> CC linux-mm in case somebody has a good answer but missed this in lkml traffic
> >>
> >> On 01/23/2015 11:18 PM, John Moser wrote:
> >>> Why is there no tunable to OOM at low page cache?
> > AFAIR, there were several trial although there wasn't acceptable
> > at that time. One thing I can remember is min_filelist_kbytes.
> > FYI, http://lwn.net/Articles/412313/
> >
> 
> That looks more straight-forward than http://lwn.net/Articles/422291/
> 
> 
> > I'm far away from reclaim code for a long time but when I read again,
> > I found something strange.
> >
> > With having swap in get_scan_count, we keep a mount of file LRU + free
> > as above than high wmark to prevent file LRU thrashing but we don't
> > with no swap. Why?
> >
> 
> That's ... strange.  That means having a token 1MB swap file changes the
> system's practical memory reclaim behavior dramatically?

Basically, yes but 1M is too small. If all of swap consumed, the behavior
will be same so I think we need more explicit logic to prevent cache
thrashing. Could you test below patch?

Thanks.