Messages in this thread | | | From | "Doug Smythies" <> | Subject | RE: [PATCH] cpuidle: Add 'high' and 'low' idle state metrics | Date | Wed, 5 Dec 2018 15:07:54 -0800 |
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Hi Rafael,
On 2018.12.03 04:32 Rafael J. Wysocki wrote:
> Add two new metrics for CPU idle states, "high" and "low", to count > the number of times the given state had been asked for (or entered > from the kernel's perspective), but the observed idle duration turned > out to be too high or too low for it (respectively).
I wonder about the "high" "low" terminology here.
> These mertics help to estimat the quality of the CPU idle governor > in use.
Yes, very useful. Thanks.
Here the terms are mixed with "deep" and "shallow"
> + unsigned long long high; /* Number of times it's been too deep */ > + unsigned long long low; /* Number of times it's been too shallow */
> +``high`` > + Total number of times this idle state had been asked for, but the > + observed idle duration was too short to match its target residency. > +
O.K. To avoid ambiguity, how about naming them "too_short" and "too_long"?
> +``low`` > + Total number of times this idle state had been asked for, but a deeper > + idle state would have been a better match for the observed idle duration.
Even though I read the patch, by the time I actually looked at the numbers I had forgotten the meaning. I had look at idle state 0 and 4 (the deepest for my computer) to figure it out:
doug@s15:~/c$ cat /sys/devices/system/cpu/cpu0/cpuidle/state0/low 259871 doug@s15:~/c$ cat /sys/devices/system/cpu/cpu0/cpuidle/state0/high 0 doug@s15:~/c$ cat /sys/devices/system/cpu/cpu0/cpuidle/state4/low 0 doug@s15:~/c$ cat /sys/devices/system/cpu/cpu0/cpuidle/state4/high 5584
Because state 0 can not be too short and state 4 can not be too long.
... Doug
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