I need some script that needs to do some work every 10 seconds. To do this I wrote
sleep 10
echo "do something"

Now I'm getting the feeling that this slows my system down. I guess that's because the sleep process still needs processing time to do nothing. Is this true? And if so what is a better way to do this ?

This script needs to be run in the background

Depending on what you're getting the system to do in terms of closing down processes once finished, it shouldn't be that much of a problem, but what is you need executing every 10 seconds? A more elegant solution would be to execute your script via cron, but the lowest interval would be every minute, I don't think you can specify it to run every x seconds.

the thing I need to execute is a nsupdate do update the record on my DNS server

Do you really need your client updating every 10 seconds? I think a cronjob running every minute might be more reasonable, maybe not even that often... What is it you have running on your machine that requires such frequent communication with your DNS server?

I realise it sounds a bit like overkill (well a lot) but I have my reasons. It all fits in one application that needs high performance and can't be down for more than 20 seconds.

Okay, so a backgrounded script is about all I can think of at those intervals, though I still don't understand your environment. nsupdate shouldn't cause any memory leaks that would build up + up causing the system to slow down.

Could you elaborate a little more on what you mean when you say the system slows down, and also include the script you've written, along with how you're starting this script?

If you want ten-second resolution, I think that what you are doing now is reasonable: one process (group), that continues to exist, that sleeps at regular intervals.

When a process "sleeps," it simply becomes non-dispatchable for ten seconds. When the timer interrupt goes off, the process gets placed on the runlist again. There's no overhead in doing that. It isn't "slowing the system down."

It would actually be slightly more expensive to rely upon cron, because a new process is constantly being created, every ten seconds. That's unnecessary here, imho...

Thanks for your answers. I guess the slowing down must have another reason.