Swap partition - how big?

Forum: HD Install
Topic: Swap partition - how big?
started by: LancerNZ

Posted by LancerNZ on June 27 2005,08:32

Okay - now that I've installed to my HD, I'm thinking i should have made a swap partition as performance can be slow on tis old notebook (I think 8mb RAM but not sure).

Question 1: How do I get system info of my box regarding RAM, CPU spec etc?
Question 2: How do I figure out the ideal swapfile / partition size for the same machine?
Question 3: Can I use something like fdisk to add a swapfile nondestructively or will this require a reinstall from scratch?

Posted by skaos on June 27 2005,15:22

If you really only have 8 MB, I would suggest that you try Basic Linux (http://distro.ibiblio.org/pub/linux/distributions/baslinux/) as DSL requires more than 8 MB (I'm not sure, but DSL may be possible to boot into command line).

Q1:
Download tomsrtbt (http://www.toms.net/rb/), create a diskette, boot and run these commands:
free
more /proc/meminfo
more /proc/cpuinfo
dmesg | more
fdisk -l

Q2:
An old rule of thumb says that swap should be twice physical ram.

Q3:
If there is some free space on the disk not used for a partition, it is possible. Otherwise, no.

Posted by LancerNZ on June 28 2005,19:06

Thanks.

Looks like I actually have 36Mb RAM in this thing and around a 100Mhz CPU. Seems to be zipping along reasonably well after adding some 74Mb or so swap.

Posted by tjm4fun on June 28 2005,20:29

The general rule of thumb with swap is 2x your ram.
I've found alot depends on the size and number of apps you have open.
for a machine with 36 meg I would advise at least 128 m, 256 m if you have the space, cause you're gonna run out of real ram pretty quick.
If you;re doing ok, tho, I would leave it till a problem shows up and then make the change.
Also be sure you are using the swap, if it wasn;t formatted as swap when you booted, it won;t be using it.
To format for swap open a root window, or add sudo in front of this:
mkswap /dev/hdax

where you would substitute your actual hda device number.
The when done issue:
swapon

or sudo swapon if you don;t have root auth.
It will start using the swap right away, and will automatically use it on each subsequent reboot.
Good luck!