Re: cpuidle - minimum time for sleep

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 10/09/2014 02:01 PM, Valdis.Kletnieks@xxxxxx wrote:
> On Thu, 09 Oct 2014 21:28:23 +0300, Ran Shalit said:
> 
>> 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 majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Arm (vger)]     [ARM Kernel]     [ARM MSM]     [Linux Tegra]     [Linux WPAN Networking]     [Linux Wireless Networking]     [Maemo Users]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Trails]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux