From: Minchan Kim <minchan@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: John Moser <john.r.moser@gmail.com>,
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>
Subject: Re: OOM at low page cache?
Date: Wed, 28 Jan 2015 15:26:10 +0900 [thread overview]
Message-ID: <20150128062609.GA4706@blaptop> (raw)
In-Reply-To: <54C77086.7090505@suse.cz>
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/
> >
> > I have no swap configured. I have 16GB RAM. If Chrome or Gimp or some
> > other stupid program goes off the deep end and eats up my RAM, I hit
> > some 15.5GB or 15.75GB usage and stay there for about 40 minutes. Every
> > time the program tries to do something to eat more RAM, it cranks disk
> > hard; the disk starts thrashing, the mouse pointer stops moving, and
> > nothing goes on. It's like swapping like crazy, except you're reading
> > library files instead of paged anonymous RAM.
> >
> > If only I could tell the system to OOM kill at 512MB or 1GB or 95%
> > non-evictable RAM, it would recover on its own. As-is, I need to wait
> > or trigger the OOM killer by sysrq.
> >
> > Am I just the only person in the world who's ever had that problem? Or
> > is it a matter of questions fast popping up when you try to do this
> > *and* enable paging to disk? (In my experience, that's a matter of too
> > much swap space: if you have 16GB RAM and your computer dies at 15.25GB
> > usage, your swap space should be no larger than 750MB plus inactive
> > working RAM; obviously, your computer can't handle paging 750MB back and
> > forth. If you make it 8GB wide and you start swap thrashing at 2GB
> > usage, you have too much swap available).
> >
> > I guess you could try to detect excessive swap and page cache thrashing,
> > but that's complex; if anyone really wanted to do that, it would be done
> > by now. A low-barrier OOM is much simpler.
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?
Anyway, I believe we should fix it and we now have workingset.c so
there might be more ways to be smart than old(although I am concern
about that shadow shrinker blows out lots of information to be useful
to detect in heavy memory pressure like page thrashing)
Below could be band-aid until we find a elegant solution?
next prev parent reply other threads:[~2015-01-28 6:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <54C2C89C.8080002@gmail.com>
2015-01-27 11:03 ` OOM at low page cache? Vlastimil Babka
2015-01-28 6:26 ` Minchan Kim [this message]
2015-01-28 12:36 ` Rik van Riel
2015-01-28 14:13 ` John Moser
2015-01-28 14:15 ` John Moser
2015-01-29 1:24 ` Minchan Kim
2015-01-28 14:27 ` John Moser
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