Ram full -> system freeze

[KIA]aze · 04-30-2007, 07:58 AM

Hi,

I am using Ubuntu Gutsy Gibbon on a compaq presario with 448MB of RAM (512-64 from shared video mem) and a 2.4GHz Pentium 4.
My swap partition is 1GB big and it's on an extended partition (the same as Ubuntu).

In the last days, I frequently had a problem of my RAM getting filled up ending up with a pseudo-freeze of the system:
-I can't move the mouse correctly anymore (it moves from time to time).
-I can't open a virtual terminal because of the same reason and when it finally comes up, I can't type my login+password+ps+killall.

Basically, everything gets so slow that the system is unusable.

Moments when it happened:
-while exporting a 12MB Openoffice presentation to PDF (acceptable)
-when adding a new C++ file to eclipse!! (which is horribly slow generally)
-while using Lyx, Amarok, gnome PDF viewer, open-office and 1 or 2 Nautilus windows

Right now, my laptop is next to me frozen while "building" GHCi library"...

*Is there any way to force Linux to leave enough RAM available so the system remains controllable?
*Could it have something to do with the swap being on an extended partition?
*Or is it a Gutsy Gibbon related problem (gutsy being the new testing version of Ubuntu)?

*And is there an equivalent to the ctrl+alt+del from windows to reboot the PC?
(reaction to ctrl+alt+backspace is also so slow that it's useless)

macemoneta · 04-30-2007, 10:28 AM

Some basic realities:

- swap is bad
- disk drive are very slow compared to RAM
- laptop hard drives are slow compared to desktop hard drives
- RAM is very inexpensive these days (1GB for as little as $60 USD)

One tuning possibility is to increase the swappiness of the system, so more gets moved to swap earlier. This will reduce the large transfers and thrashing that occurs when frames are depleted.

Try these settings as a starting point:

Code:

echo "0" > /proc/sys/vm/laptop_mode
echo "500" > /proc/sys/vm/dirty_writeback_centisecs
echo "2000" > /proc/sys/vm/dirty_expire_centisecs
echo "20" > /proc/sys/vm/dirty_ratio
echo "80" > /proc/sys/vm/swappiness

No need to reboot; the changes take effect immediately, but need to be reset after a reboot.