linux-kernel - Re: rsync: page allocation stalls in kernel 4.9.10 to a VessRAID NAS

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Message-ID: <20170228144045.GD26792@dhcp22.suse.cz>
Date:   Tue, 28 Feb 2017 15:40:46 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Robert Kudyba <rkudyba@...dham.edu>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: rsync: page allocation stalls in kernel 4.9.10 to a VessRAID NAS

On Tue 28-02-17 09:33:49, Robert Kudyba wrote:
> 
> > On Feb 28, 2017, at 9:15 AM, Michal Hocko <mhocko@...nel.org> wrote:
> > and this one is hitting the min watermark while there is not really
> > much to reclaim. Only the page cache which might be pinned and not
> > reclaimable from this context because this is GFP_NOFS request. It is
> > not all that surprising the reclaim context fights to get some memory.
> > There is a huge amount of the reclaimable slab which probably just makes
> > a slow progress.
> > 
> > That is not something completely surprsing on 32b system I am afraid.
> > 
> > Btw. is the stall repeating with the increased time or it gets resolved
> > eventually?
> 
> Yes and if you mean by repeating it’s not only affecting rsync but
> you can see just now automount and NetworkManager get these page
> allocation stalls and kswapd0 is getting heavy CPU load, are there any
> other settings I can adjust?

None that I am aware of. You might want to talk to FS guys, maybe they
can figure out who is pinning file pages so that they cannot be
reclaimed. They do not seem to be dirty or under writeback. It would be
also interesting to see whether that is a regression. The warning is
relatively new so you might have had this problem before just haven't
noticed it.
-- 
Michal Hocko
SUSE Labs