Huge instability and insanely large memory footprint in 9.04

Marius Gedminas marius at pov.lt
Fri Sep 25 11:40:26 UTC 2009


On Fri, Sep 18, 2009 at 04:46:21AM -0700, J. Lennard wrote:
> First I'm sorry to write what may appear as a rant, but I hope it is
> not considered so. I'm writing to express huge instability problems in
> Ubuntu 9.04. I migrated from ubuntu 8.04 (386) to ubuntu 9.04 (amd64)
> using a simple clean install.
...
> I don't really know where to start. During past month, my machine
> constantly went to trashing mode where the hard-disk light is
> constantly on and I can't access anything or even swtich to linux
> console for several *minutes*. This has occured more than four times
> although all I usually run is a pdf viewer, an mp3 player, emacs, and
> firefox with simple html pages (not even gmail, flash, etc).

Do you have any swap space?

I've got an Asus EeePC 900 with 1 GB of RAM.  Twice now I've experienced
the same thing: constant disk I/O, huge latencies for any desktop task
(switching windows, launching terminals).  I suspect a bug in the Linux
VM subsystem, since *I was not running out of memory*.  Usually about
40-50% of my RAM is in disk cache---I keep track of memory usage via a
GNOME panel applet.  On those occasions cache size was shrinking,
completely free memory was increasing, all application pages were being
constantly swapped out and back in causing constant disk I/O (which is
painful on an SSD).  The fix was to create a temporary swap file in
/tmp:

  sudo -s
  dd if=/dev/zero of=/tmp/swapfile bs=1M count=1024
  mkswap /tmp/swapfile
  swapon /tmp/swapfile

Instantly the system became responsible again, after using ~400
*kilobytes* of swap.

I can only assume that having 0 swap space confused the VM somehow and
kicked it into a full-on panic "let's free all the ram we can" mode.

This swap file disappears after a reboot, and so far the problem hasn't
recurred, so I didn't bother setting up a permanent swap partition (I'm
afraid to destroy my SSD too quickly with constant writes---this already
happened once thanks to ext3's journal).

I did have a new weird VM problem yesterday: for some reason, despite
having 250 megs totally free, the kernel went into OOM-killer mode and
killed rhyhmbox and chromium-browser, then, thankfully, stopped.

It saddens me that all I have are anecdotes rather than informative bug
reports. :(

> I can't really understand how this can happen. Several times, and
> after a day or two of use, firefox, with *one* simple html tab open
> took 340+ MBs; that's insane. Evince took 120MB while only a single
> pdf file was open. Even Xorg was taking RAM around a hundread
> megabyte.[1]
>
> [1] Resident set memory, not virtual memory.

RSS includes shared pages too, giving a skewed picture.  Xorg's memory
maps include mmaped device address space, giving an even-more skewed
picture.

> The final result? a machine constantly thrashing and basically
> unusable. I ran this on a core2 laptop with a full 1GB of ram. How
> come the experience is SO bad in supposedly a *stable* distro?

Software is hard.

> The second problem is that the GUI is *really* slow, and I use *zero*
> visual effects. Switching between workspaces is very sluggish where I
> see parts of firefox in my audacious window for about half a second
> while switching between workspaces. Switching between applications
> (alt+tab) is not smooth at all.

*Using* desktop effects will give you smoother desktop/application
switching.  That's the primary reason I enable them, it results in the
whole desktop being double-buffered and therefore reduces redrawing
artifacts such as these.

What kind of graphics do you have?  My puny little Asus with its Intel
945 was very sluggish until I disabled vertical synchronisation.

> The third thing, which is disastrous and never occurred to me before
> using Ubuntu (and I've been using Ubuntu since Ubuntu 5) was constant
> and *systematic* audio skipping while doing *any* task. Heck, I swear
> simple switching between workspaces sometimes lead to several audio
> skipping.

If this happens during the thrashing, then it's understandable; if not
then *ouch*.

> I re-installed a Ubuntu 8.04 amd64 and my sanity is back.

You said you were running 8.04 386 before?  amd64 versions generally
need more RAM, and their primary advantage starts showing up on machines
with at least 4 GB of RAM.

> I'm sorry, this is my worst Linux experience ever, but thankfully
> Ubuntu 8.04 works beautifully here that I'm thankful after all. It's
> really sad my favourite OS reached this level of instability and
> bloat, but hey, I at least have 8.04 till 2011, which I couldn't ask
> for more.
> 
> Please don't let Ubuntu go to this sad path.
> 
> Thank you.

Marius Gedminas
-- 
Suppose you went back to Ada Lovelace and asked her the difference between a
script and a program. She'd probably look at you funny, then say something
like: Well, a script is what you give the actors, but a program is what you
give the audience.
                -- Larry Wall
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <https://lists.ubuntu.com/archives/ubuntu-devel-discuss/attachments/20090925/461259c5/attachment.sig>


More information about the Ubuntu-devel-discuss mailing list