[Gllug] Memory usage when idle

[Daniel P. Berrange]

On Wed, May 05, 2004 at 12:33:23PM +0100, NorthLondon John wrote:
> Hi,
> 
> The story so far: I've installed Debian on an old laptop (266mhz, 
> 64mb), and performance is abysmally slow. Not expecting blindingly 
> fast, ram is the bottleneck (planning on bumping the memory up), but X 
> is almost unusably slow.
> 
> For the purposes of comparison, I have my Slackware laptop up as well, 
> both boxes have x, gnome 2.4 and system monitor running, and nothing 
> else

Have you disabled the 10's of background processes most distros start
automatically like cron, gpm, atd, lpd, etc, etc, etc. These can
have a surprisingly big impact.

Having just upgraded to Fedora I can say that in comparison to a simple
Window manager like WindowMaker, Gnome is a horrific memory hog - if you
don't need GNOME window manager then switch to a lightweight one. Also
get rid of any background image in your desktop - that sucks memory 
quite significantly.

> Slackware; used memory 29.6 mb
> Debian: used memory 59.0 mb

Is this including or excluding the mmemory used by the kernel
disk cache - the kernel will tend to use all available memory
to cache pages from the disk to maximise I/O performance[1]

> 
> Slack has one instance of agetty running (memory use; 468k), whilst 
> debian has 6 instances of getty (each using 1.5mb)

Be wary of doing the simple math '6 x 1.5mb = 9mb' here because much of
that memory will be shared across all six processes - so if, for example,
1.2 mb of this were shared the combined usage would merely be 
'6 x 0.3 + 1.2 = 3mb'. Of course accurately figuring out shared usage
across all processes on your system is nigh on impossible - particularly
if any are multi-threaded.

That said, you could try switching debian to using agetty to see if
that has comparable memory usage to slackware. And if you don't need
6 virtual consoles, then edit inittab to reduce the number of getty
launched to 2 or 3.

> Slack: Mixer-applet: Slack 7.3mb, Deb 13.8mb.
> 
> Background processes and memory usage seem pretty excessive. Where do I 
> go from here?

Recompile the kernel removing anything you don't need.

Checkout an alternative distribution optimized for low memory
usage.

Dan.

[1] Of course this doesn't always go to plan because maximising
    I/O performance in this way impacts on applications responsiveness
    as they get swapped in/out....


-- 
|=-               http://www.berrange.com/~dan/gpgkey.txt             -=|
|=-   berrange at redhat.com  -  Daniel Berrange  -  dan at berrange.com    -=|
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