Solaris

Hi jlliagre,

Thanks for your reply.

For q1) Yeap, when i run a sar -q 1 60 (for 1 minute average), the run queue's average is about 1+ , but my load avg for 1 minute (using uptime) shows only about 0.13.
Reading Brendan Gregg 's load average video - seems to talk about exponential decay of the load calculation (but i am no maths expert).
Thus, i will leave it as it is -> that having a load of 1 for a minute, will require more then 1 minute to be reflected in the " 1 minute load average " .

For q2) I am still confuse about the difference between CPU load and CPU utilization.

(on a 1 cpu - no multicore, or hyperthread computer)
If i have a continuous load of 1 for 1 minute, does that means my CPU utilization is near 100% / 0% idle for that 1 minute ?

q3) You mentioned that CPU load is sampled at 10ms interval.
How about the sampling interval for CPU utilization/time ?

In a nutshell, if i have 6 core cpu (12 thread total), and i have a average load of 3 most of the time;
Can i expect my CPU utilization to be around 3/12 * 100 = 25% (when the load is 3) ?

p.s. 1 last question -> does sar -q include thread currently running in cpu or only those runnable/ready in run queue ?

Regards,
Noob

It might mean that, but not necessarily. Could be also ten processes all repeating this pattern : fighting to get the CPU during 1 second then idling for 9 seconds.
There is no sampling. The CPU utilization is accurately measured, not estimated.
That's only one eventuality.
The latter. A running thread is not waiting in a queue.

Hi Jilliagre,

Once again, thanks for your reply and truly appreciate your time.

q1) Do you mean the 10 processes fighting to get the CPU at the same time ?
I would then expect to see a load of 9 (in queue) + 1 (running) and have 100% CPU utilization for that 1 minute.

- Am I right ?

q2) Can you elaborate on this further ? Why is it 1 ?

q3) Should hyperthreading be taken into consideration when measuring load ?
- 6 core ; point of saturation -> 6 (can take load up to 6) or
- 6 core but 12 thread; point of saturation -> 12 (can take load up to 12)

Regards,
Noob

No. The load would be 9+1 during the same 1 second when all processes compete then 0 during 9 seconds when all are idling so the average load would be 1. As you have only one core, the CPU utilization would be 10%.
See q1.
It should but an issue is depending on the kind of workload, the saturation level will vary. See for example CPU utilization of multi-threaded architectures explained (Solaris and Systems Information for ISVs)