Discussion:
cpuidle - minimum time for sleep
Ran Shalit
2014-10-09 18:28:23 UTC
Permalink
Hello,

Does anybody know what is the minimum expected time for sleep period
with the cpuidle ?

I intend t use the menu governer, and I try to estimate the sleep time.

Thanks,
Ran
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to ***@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
V***@vt.edu
2014-10-09 19:01:43 UTC
Permalink
Post by Ran Shalit
Does anybody know what is the minimum expected time for sleep period
with the cpuidle ?
Both processor dependent and sleep level dependent. There's a certain
amount of latency induced by the hardware waking up.

Look at /sys/devices/system/cpu/cpu*/cpuidle/state*/latency
Nishanth Menon
2014-10-09 19:20:39 UTC
Permalink
Post by V***@vt.edu
Post by Ran Shalit
Does anybody know what is the minimum expected time for sleep period
with the cpuidle ?
Both processor dependent and sleep level dependent. There's a certain
amount of latency induced by the hardware waking up.
Look at /sys/devices/system/cpu/cpu*/cpuidle/state*/latency
Yes, that is correct. the sleep and wakeup time are dependent on the
power state we attempt (may or maynot achieve)

I personally toggle an unused pin using padmux register write with
weak pull up/down in controlled tests (mostly using disable =1 for
states I am not measuring), then capture pinctrl toggles using [1]
into a csv for many thousands of iterations then use the conservative
values. I usually do this at the slowest frequency to capture the
worst case values that i feed into cpuidle_driver.states.exit_latency
and appropriate value for target_residency - I usually ignore
power_usage as the value is never a constant and depends on quiet a
few factors that i cannot discuss in public domain.

Here are some helpful links on OMAP specific strategies (these may be
a little old, but just search for CPUIDLE latency measure in google)

https://lwn.net/Articles/384146/

http://www.omappedia.org/wiki/Power_Management_Device_Latencies_Measurement

http://lists.linaro.org/pipermail/linaro-dev/2010-August/000568.html


[1] https://www.saleae.com/
--
Regards,
Nishanth Menon
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to ***@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
manty kuma
2014-10-10 03:22:55 UTC
Permalink
Post by V***@vt.edu
Post by Ran Shalit
Does anybody know what is the minimum expected time for sleep period
with the cpuidle ?
By sleep period do you mean sleep time for complete device or only for
cpu's? If you want to check for device as a whole, you can see the print in
the kernel log. If you want to check programmatically,
suspend_devices_and_enter() is the function.
Post by V***@vt.edu
Post by Ran Shalit
Does anybody know what is the minimum expected time for sleep period
with the cpuidle ?
Both processor dependent and sleep level dependent. There's a certain
amount of latency induced by the hardware waking up.
Look at /sys/devices/system/cpu/cpu*/cpuidle/state*/latency
_______________________________________________
Kernelnewbies mailing list
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Loading...