[plug] Invisible swap?

[Bernard Blackham]

Plug,

No problems here for now, just sheer curiosity. Why does the
following work:

My machine has 256MB RAM, and 512MB (roughly) of swap space. I fire
up mozilla, openoffice, amongst others, and I get the following:

# free
             total       used       free     shared    buffers     cached
Mem:        257124     250228       6896          0      11480     128572
-/+ buffers/cache:     110176     146948
Swap:       498004     135712     362292

Out of curiosity, I type

# swapoff -a
and a few seconds later it returns with no errors. free shows

# free
             total       used       free     shared    buffers     cached
Mem:        257124     252444       4680          0       9100      69260
-/+ buffers/cache:     174084      83040
Swap:            0          0          0

Note that used memory went up by about 2MB, buffers/cache went up
by 64MB, and used swap fell by roughly 135712KB...

And the machine works perfectly still. So was most of that 135MB of
apparently used swap not really doing anything? If whatever was in
swap wasn't needed, can similar be said for what is actually in
memory? Do I infact even need swap if I want to open up several huge
apps whilst doing kernel compiles?

So many questions. Any enlightenment is welcome :)

TIA,

Bernard.

-- 
 Bernard Blackham
 bernard at blackham dot com dot au
 Australian Linux Technical Conference 2003: http://www.linux.conf.au/