Re: backing up ext4 fs, system unresponsive, thrashing like crazyeven though swap is unused

From: Dimitrios Apostolou
Date: Thu Dec 06 2012 - 10:15:55 EST


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.


Thanks,
Dimitris

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