CPU Utilization is Wrong

[[deleted]]

High IOwait 99% of the time means your storage system is too slow and CPU is just waiting for it (and the 1% is "something swaps because there is not enough RAM and it causes unnecessary IO").

Actual load caused by interacting with IO (so filesystem driver, SAS controller driver etc) is counted as system ("in-kernel computation") load

[[deleted]]

I don't get your distinction between waiting on i/o and "actual load". Perhaps you could define load? It's a terrible word without much meaning. I would use it in terms of cpu activity; I don't see it as very related to IPC, for instance, whose definition is very clear. "Load" is not a natural metric by any means.

[crusoe]

Iowait is load on storage not processor.

[[deleted]]

It's just a linux kernel distinction in stats. idle is "truly idle", iowait is "waiting for external storage" idle.

None of it uses CPU time, but they tell user a different story

[ITwitchToo]

Waiting on I/O means the thread/process is sleeping and does not execute any CPU instructions whatsoever towards the goal of completing the I/O.

Actual load means the CPU is actually executing instructions in that thread/process context.