> As a set of three, you can tell if load is increasing or decreasing
That could be accomplished with a set of two.
A set of three could in theory give you acceleration.
That could be accomplished with a set of two.
A set of three could in theory give you acceleration.
The most recent 2 data points give you is whether the problem is currently getting worse, getting better or steady. The third gives you a sense of whether it has been doing on a while.
"Three figures are better than just the last one, because from these the user can predict the trend as well as note local variation."
I think that depends on the sampling frequency, doesn't it? (given a modern OS with lots and lots of threads and processes)
Think of it as being like traffic. Analytically it is easy to think of smoothly varying speeds. Reality is that there is a car accident, then a sudden traffic jam. We are poking around to figure out where and when that traffic jam happened. And sometimes the cars get cleared off the road and by the time we begin looking the jam is already evaporating.
So comparing the 1 min and 5 min load averages tell us whether the jam is getting worse, holding steady, or improving on its own. Looking at the 15 minute one tells us whether this happened recently.
Performance tends to degrade rather...rapidly when you start to actually meaningfully swap actual working memory. With modern quantitys of RAM I'd almost prefer to just run swapless and let the system OOM so it can just be rebooted and get on with it...
https://www.youtube.com/watch?v=1bNOO3xxMc0
The point he makes arises from basic queue theory and is applicable to all kinds of systems, and how those systems react to load. It's got little to due with particular hardware and everything to do with basic math.