topic Re: swap memory in Operating System - Linux

swap memory

admin1979 — Thu, 06 May 2010 08:13:30 GMT

Hi,

We have SuSE Linux 9.0 on a old system.
Recently we had few problems with this system. The system becomes unresponsive regularly. Then we hard boot and the sytem come back again.
We suspect its a memory issue. It has 500 MB Phy RAM and 1 GB of swap. But most of the time the free memory is in the range of 50 MB - 8 MB. We also noticed that the system is not at all using the SWAP space allotted.

Here are the facts,

# cat /etc/fstab
/dev/hda3 / ext3 acl,user_xattr 1 1
/dev/hda1 /boot ext2 acl,user_xattr 1 2
/dev/hda4 /usr ext3 acl,user_xattr 1 2
/dev/hda2 swap swap pri=42 0 0
devpts /dev/pts devpts mode=0620,gid=5 0 0
proc /proc proc defaults 0 0
sysfs /sys sysfs noauto 0 0

# free -m
total used free shared buffers cached
Mem: 494 486 7 0 97 132
-/+ buffers/cache: 256 238
Swap: 1027 0 1027

# cat /proc/swaps
Filename Type Size Used Priority
/dev/hda2 partition 1052248 0 42

Do you also think that its the memory/swap issue?

If yes then how do we make the system use the swap space?

Please suggest.

Thanx,
admin

Re: swap memory

Srimalik — Thu, 06 May 2010 09:35:29 GMT

High memory usage and not using swap is not a problem for linux, the memory is used for buffers and will be freed when you need it for applications.

Re: swap memory

J. Maestre — Thu, 06 May 2010 16:30:05 GMT

Check the "-/+ buffers/cache" line, you actually have 238 free MB, not counting cached stuff (which will be freed as soon as it's needed by a running process). That's quite reasonable for a 500MB system.

Regarding the use of swap, you can change that throught /proc/sys/vm/swappiness, but if anything you would want a low value there so the system uses as few swap as possible, as long as it's not really needed.

Long story short: your issues have nothing to do with the amount of free memory, or at least not with the memory usage you have posted.

Re: swap memory

Ivan Ferreira — Thu, 06 May 2010 18:33:58 GMT

I suggest you to install collectl or at least enable sar. Collecting performance statistics would help to diagnose the problem.

If the system is totally unresponsive, then you may have a hardware problem, you should check the messages file and dmesg output.

Re: swap memory

admin1979 — Thu, 02 Sep 2010 06:24:37 GMT

As mentioned above.