On 05/14/18 08:39, Christopher Lameter wrote:
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?
The following article explains why it probably made sense in 1993 to
include TASK_UNINTERRUPTIBLE in loadavg and also why this no longer
makes sense today:
http://www.brendangregg.com/blog/2017-08-08/linux-load-averages.html
Bart.
