Why does mpstat show different values when I use the interval setting?
- by Abe
Here's the output I get when I run mpstat:
$mpstat
Linux 3.2.0-30-generic (my-laptop-C650) 09/17/2012 _x86_64_ (2 CPU)
05:32:01 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle
05:32:01 PM all 9.16 0.08 2.69 2.00 0.00 0.04 0.00 0.00 86.02
And here's what I get when I run it with a one-second interval:
$mpstat 1
05:31:51 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle
05:31:52 PM all 1.52 0.00 1.01 0.00 0.00 0.00 0.00 0.00 97.47
05:31:53 PM all 2.04 0.00 1.02 0.00 0.00 0.00 0.00 0.00 96.94
05:31:54 PM all 1.50 0.00 1.50 0.00 0.00 0.00 0.00 0.00 97.00
Why does the first process show the processor as 86% idle, and the second show it as ~97% idle? I've tried this in a bunch of different configurations, and it's not a real difference in CPU usage -- unless mpstat itself is making the difference.
Which number should I trust?
