Re: [PATCH 0/7] psi: pressure stall information for CPU, memory, and IO

Christopher Lameter
2018-05-14T15:39:33Z

On Mon, 7 May 2018, Johannes Weiner wrote:

> What to make of this number? If CPU utilization is at 100% and CPU
> pressure is 0, it means the system is perfectly utilized, with one
> runnable thread per CPU and nobody waiting. At two or more runnable
> tasks per CPU, the system is 100% overcommitted and the pressure
> average will indicate as much. From a utilization perspective this is
> a great state of course: no CPU cycles are being wasted, even when 50%
> of the threads were to go idle (and most workloads do vary). From the
> perspective of the individual job it's not great, however, and they
> might do better with more resources. Depending on what your priority
> is, an elevated "some" number may or may not require action.

This looks awfully similar to loadavg. Problem is that loadavg gets
screwed up by tasks blocked waiting for I/O. Isnt there some way to fix
loadavg instead?