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SubjectRe: backing up ext4 fs, system unresponsive, thrashing like crazy even though swap is unused
On 2012-11-25 Sunday at 21:30 +0200 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!

Hello Dimitrios,

I would try a 2.6.27.* kernel, for following reasons:

(1) Kernel development since 2.6.27 achieved significant performance
improvements at the cost of exploding memory consumption by the kernel for
_internal_ data structures. I am currently using a 3.2.34 kernel on a Notebook
with 4 G RAM. 0,5 … 1 G RAM is usually occupied just by kernel slab [1]; this
memory cannot be swapped, it cannot be released by other means than rebooting,
and there seems to be _no_ adjustment to memory pressure. I am surprised,
that you have managed to boot a 3.6.* kernel at all with only 128 M RAM.

(2) At the time, when I used a PIII-Notebook, kernels 2.6.27 to 2.6.29 where
current. Thus chances are good, that a 2.6.27.* kernel will support chipset,
PCI bus and devices of your notebook. 2.6.27 got longterm maintainance, the
latest release in the linux-stable git repository is 2.6.27.62.
So Q @ LKML community:
Does anybody know a x86 distribution or live-CD using a 2.6.27.* kernel?


[1] Picture described in my LKML message
Date: Fri, 20 Jan 2012 01:08:00 +0100
Subject: Re: [kmemleak report 1/2] kernel 3.1.6, x86_64: mm, xfs ?, vfs ?
remained the same with _every_ 3.1.* and 3.2.* kernel tried so far.


--
Roland
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