Linode graphs show CPU maxed out, but OS shows the exact opposite
I just got an alert from Linode of CPU pegged at an average of 108.6%. Looking at the chart, it looks like it's been this way for a bit and is ongoing.
However, htop, top, etc., all show usage at an otherwise expected state, which is far below that. At the time of writing, no CPU is being used more than 12% and that's only for little blips. The average is far lower.
Looking into the processes, I see nothing particularly telling.
Any ideas?
5 Replies
some system calls are really cheap for the guest but can't or haven't been hardware accelerated so are expensive for the host. If there's a lot of those system calls, the guest can show no load and the host 100%.
Minecraft is known to trigger it.
jtoscani
Linode Staff
We receive the statistics displayed in your graph from the host machine. It's rare, but sometimes the results provided aren't accurate and there's a discrepancy. When in doubt I would go with the output of htop and top, as those would show your true CPU usage.
@crashbunny How would one determine whether or not this is the case? Should one even be concerned? And is there any way to mitigate this?
Short answer, i don't know @wxl
I've only heard of minecraft triggering high host load while guest load is low, and only certain versions of it.
https://bugs.mojang.com/browse/MC-183518
has lots of good info on how they tracked down the minecraft issue, using dstat and syscount-perf
That's plenty helpful @crashbunny. Thank you kindly.
It is also good to know that the Linode graphs essentially measure physical/host resources rather than virtual/guest resources. I learned something and that's always a good thing. :)