Derek Broughton derek at
Thu May 14 20:15:58 BST 2009

Goh Lip wrote:

> I have 2 GB RAM, had 7.5 GB swap (yes, some time ago partitioned my
> disk, thought it safer than sorry, still no regrets, have more disk
> space than I could use).

A perfectly sound strategy these days.

> Jaunty 64
> KDE 4.2.3
> Linux 2.6.28-11
> Noticed at system monitor (always running), that my swap usage is ALWAYS
> zero, whatever I do, Gimp, Firefox,  Kaffeine all running.
> Checked /etc/fstab to make sure swap is there, enabled and on, (swapon
> -a); even when flash 10 freezed temporarily firefox, swap is still zero.
> Is it because swap is not needed?

It's either because swap isn't needed or the monitor you're using is buggy 

> Can my computer can handle all this without swap?

I wouldn't have thought so.  I have 3GiB real memory (still trying to figure 
out why it isn't 4, as everything I've read says I just need to use the PAE 
enabled kernel to use all 4GiB) and it's rarely using more than 2GiB of 
_virtual_ memory, but still some of that is always in swap space.  Right now 
I am using less than half my real memory, but there's still 700K of swap 

> I also note though, that my RAM is never at 100% and my
> processors were never at 100%. (Flash 10 freezes 1 core at 100%, the
> other never at 100 %)

Then you probably really aren't using the swap space.  Incidentally things 
like flash are why I love dual core processors.  It's _really_ nice finally 
to actually be able to have a responsive system when something goes amok and 
hogs 100% of a CPU.
> Next, suspend to disk, (now I know the distinction from suspend to RAM,
> thanks). Are they useful only for laptops, where battery conservation is
> desired? What purpose would it serve for desktops?

Well, I rarely use the laptop battery, but I always use hibernate - why shut 
down, when you can hibernate?  I always hibernated my Windows Desktop 
machines, too.  That becomes less of an issue as boot & shutdown times are 
optimized, while memory sizes increase - it can take almost as long to 
hibernate/resume as to shutdown/restart.  I also have environmental 
objections to leaving home computers on 24/7.
> Indeed, if we have suspend to RAM in laptops, what advantage would
> suspend to disk have? Won't battery consumption be lower if disk is
> actually off?

Actually, the power consumption of the disk is probably irrelevant.  With 
suspend-to-ram, the disk _will_ be shut down.  With suspend-to-disk, the 
whole system is turned off.  The difference is in the power requirement for 
the RAM and whatever else can't be turned off while the machine is 

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