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

[Dimitrios Apostolou]

Hi Jan, thanks for your help, with this commit I can't reproduce the 
problem. The problematic workload is no more inflating the 
ext4_inode_cache, in fact I've been able to run even heavier workloads 
with the ext4_inode_cache never surpassing 2-4MB.

Thanks everyone for helping,
Dimitris


On Thu, 6 Dec 2012, Jan Kara wrote:
> 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@xxxxxxx>
> SUSE Labs, CR
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