linux-kernel - Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority

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Date:	Tue, 2 Apr 2013 12:15:05 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Michal Hocko <mhocko@...e.cz>, Linux-MM <linux-mm@...ck.org>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rik van Riel <riel@...hat.com>,
	Zlatko Calusic <zcalusic@...sync.net>,
	Johannes Weiner <hannes@...xchg.org>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd
 reclaims at each priority

On Sat, Mar 30, 2013 at 11:07:03PM +0100, Jiri Slaby wrote:
> On 03/29/2013 09:22 AM, Michal Hocko wrote:
> > On Thu 28-03-13 23:31:18, Jiri Slaby wrote:
> >> On 03/25/2013 10:13 AM, Jiri Slaby wrote:
> >>> BTW I very pray this will fix also the issue I have when I run ltp tests
> >>> (highly I/O intensive, esp. `growfiles') in a VM while playing a movie
> >>> on the host resulting in a stuttered playback ;).
> >>
> >> No, this is still terrible. I was now updating a kernel in a VM and had
> >> problems to even move with cursor.
> > 
> > :/
> > 
> >> There was still 1.2G used by I/O cache.
> > 
> > Could you collect /proc/zoneinfo and /proc/vmstat (say in 1 or 2s
> > intervals)?
> 
> Sure:
> http://www.fi.muni.cz/~xslaby/sklad/zoneinfos.tar.xz
> 

There is no vmstat snapshots so we cannot see reclaim activity. However,
based on the zoneinfo I suspect there is little. The anon and file pages
are growing, there is no nr_vmscan_write or nr_vmscan_immediate_reclaim
activity. nr_islated_* occasionally has a few entries so there is some
reclaim activity but I'm not sure there is enough for this series to
make a difference.

nr_writeback is high during the window you record so there is IO
activity but I wonder if the source of the stalls in this case are an
IO change in the 3.9-rc window or a scheduler change.

There still is a reclaim-related problem but in this particular case I
think you might be triggering a different problem, one that the series
is not going to address.

Can you check vmstat and  make sure reclaim is actually active when
mplayer performance goes to hell please?

-- 
Mel Gorman
SUSE Labs
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