linux-kernel - Re: backing up ext4 fs, system unresponsive, thrashing like crazy even though swap is unused

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Message-ID: <20121206164312.GB21029@quack.suse.cz>
Date:	Thu, 6 Dec 2012 17:43:12 +0100
From:	Jan Kara <jack@...e.cz>
To:	Dimitrios Apostolou <jimis@....net>
Cc:	Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: backing up ext4 fs, system unresponsive, thrashing like crazy
 even though swap is unused

On Thu 06-12-12 17:15:37, Dimitrios Apostolou wrote:
> On Thu, 6 Dec 2012, Jan Kara wrote:
> >On Sun 25-11-12 21:30:00, Dimitrios Apostolou wrote:
> >>On Sun, 2012-11-25 at 15:55 +0200, Dimitrios Apostolou wrote:
> >>>on an old PIII-500MHz laptop, 128MB RAM, kernel 3.6.6, I started a
> >>>backup process (tar|xz -4, nice'd and ionice'd -c3) from ext4 on local
> >>>ATA disk to ext3 on external USB disk (USB-2.0 port on PCMCIA card).
> >>>Even though earlier system load was minimal, free memory was plenty, the
> >>>system now is unresponsive and is thrashing the disk, but the swapfile
> >>>is rarely touched.
> >>
> >>I'm now having the same experience even though I replaced xz (which
> >>needed ~50MB RAM) with gzip. Even though I feel the realtime root shell
> >>is a bit more responsive than before, the OOM killer is out killing
> >>small processes like syslog-ng and systemd-logind... The
> >>ext4_inode_cache slab is taking almost all my memory (117MB). Please
> >>advise!
> > Hmm, it seems commit 4eff96dd5283a102e0c1cac95247090be74a38ed might be
> >interesting for you. It landed in -stable kernels recently as well if I
> >remember right...
> 
> Thanks, I appreciate your help as I'm stuck in a dead end now, and
> I've been trying to write some debug hook that prints all
> ext4_inodes and the reason they are pinned (is there an easy way to
> find this out?).
> 
> So maybe there is a typo in the SHA1 sum you provided? Gitweb can't
> find it in Linus' tree.
  Strange. You are right gitweb doesn't show the SHA1 but I can see it in
my git repo I pulled from Linus. Anyway, I've attached the fix for your
convenience.

								Honza

-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR

View attachment "0001-writeback-Put-unused-inodes-to-LRU-after-writeback-c.patch" of type "text/x-patch" (3357 bytes)