topic Re: swap question in Operating System - Linux

swap question

Chakravarthi — Fri, 11 Nov 2005 02:16:45 GMT

hi,

on my machine swap is not getting used, i have even tried creating a additional swap file and added it still no luck. this is happening on 2.2 kernel.

--chakri

Re: swap question

Claudio Cilloni — Fri, 11 Nov 2005 02:37:16 GMT

but... do you get "out of memory" errors?

Re: swap question

Patrick Terlisten — Fri, 11 Nov 2005 03:22:25 GMT

Hello Chakravarthi,

can you post the output of the command "free -m"? Did you get any errors because of insufficient memory? Linux donÂ´t use swap if it not must.

Regards,
Patrick

Re: swap question

Kodjo Agbenu — Fri, 11 Nov 2005 03:22:44 GMT

Hi,

After creating the swap partition, you need to format it by using :

mkswap

Then you can mount it with :

swapon

If you want this to be done automagically at boot, add the following line in /etc/fstab :

/dev/vg01/lvswap swap swap defaults 0 0

Good lcuk.
Kodjo

Re: swap question

Ivan Ferreira — Fri, 11 Nov 2005 06:33:16 GMT

"On my machine swap is not getting used"

This should be not a problem, the problem is if the swap is too used.

Why are you worried about the use of the swap.

Re: swap question

Ralph Grothe — Fri, 11 Nov 2005 08:11:00 GMT

Why do you want your box swapping?

No seroiusly, you can check if and what swap device/file is enabled by

$ /sbin/swapon -s
Filename Type Size Used Priority
/dev/sda3 partition 1028152 79976 -1

alternatively look up in /proc

cat /proc/swaps
Filename Type Size Used Priority
/dev/sda3 partition 1028152 79976 -1

Usually, as already said by others creating and activating swap is as easy as using the two commands mkswap and swapon.

However, it could be that (for what ever reason) you have set a swapiness too low (if set at all)

Check by

# sysctl -a | grep swap

if it's set.
Also see
http://kerneltrap.org/node/3000/print

Re: swap question

Chakravarthi — Fri, 11 Nov 2005 09:41:21 GMT

i'm left with very limited physical memory, and machine is tooo slow to work

Re: swap question

Chakravarthi — Fri, 11 Nov 2005 09:41:57 GMT

free -m output

total used free shared buffers cached
Mem: 895 316 578 0 13 80
-/+ buffers/cache: 223 672
Swap: 2047 0 2047

Re: swap question

Claudio Cilloni — Fri, 11 Nov 2005 10:02:01 GMT

You have 578 MB of free memory out of 895 MB of available physical memory!
Your machine isn't using swap space because it isn't necessary.

Everything is ok.

Re: swap question

Chakravarthi — Fri, 11 Nov 2005 10:12:31 GMT

that about this??

total used free shared buffers cached
Mem: 895 876 18 0 68 48
-/+ buffers/cache: 760 135
Swap: 2047 0 2047

Re: swap question

Ivan Ferreira — Fri, 11 Nov 2005 10:26:55 GMT

Linux will always use all memory available, but not for applications, but for buffer/cache. So, you probably won't see a Linux system with 50% of memory usage.

The -+buffers line in the free command shows the free memory without buffers.

Re: swap question

Patrick Terlisten — Fri, 11 Nov 2005 16:14:24 GMT

Hi,

short answer: 135MB of 895MB memory are free and your system does not need to swap. :)

Most linux-systems have a memory usage of over >50%, but the memory is used for cache and buffers. This memory will be used if an application needs more memory.

So everythingÂ´s right. :)

Regards,
Patrick