On 1/31/20 1:05 PM, Krzysztof Kozlowski wrote:
On Mon, 27 Jan 2020 at 22:55, <lukasz.luba@xxxxxxx> wrote:
From: Lukasz Luba <lukasz.luba@xxxxxxx>
Add dynamic power coefficient into CPU nodes which let CPUFreq subsystem
register the Energy Model (EM) for the CPUs.
The 'dynamic-power-coefficient' is used for calculating the dynamic power
according to the equation in documentation [1]. The Energy Model (EM)
framework relies on calculated power and cost for each OPP. The OPP power
values come from CPUFreq driver, which registered required callback
function. The simple implementation of a CPUFREQ driver, like cpufreq-dt,
uses 'dev_pm_opp_of_register_em()' which relay on
'dynamic-power-coefficient' to calculate the power of requested OPP for the
EM [2].
The calculated values might be checked in
/sys/kernel/debug/energy_model/pd*/
$ grep . /sys/kernel/debug/energy_model/pd1/cs*/*
/sys/kernel/debug/energy_model/pd1/cs:1000000/cost:558
/sys/kernel/debug/energy_model/pd1/cs:1000000/frequency:1000000
/sys/kernel/debug/energy_model/pd1/cs:1000000/power:310
/sys/kernel/debug/energy_model/pd1/cs:1100000/cost:558
/sys/kernel/debug/energy_model/pd1/cs:1100000/frequency:1100000
/sys/kernel/debug/energy_model/pd1/cs:1100000/power:341
/sys/kernel/debug/energy_model/pd1/cs:1200000/cost:558
/sys/kernel/debug/energy_model/pd1/cs:1200000/frequency:1200000
/sys/kernel/debug/energy_model/pd1/cs:1200000/power:372
/sys/kernel/debug/energy_model/pd1/cs:1300000/cost:674
/sys/kernel/debug/energy_model/pd1/cs:1300000/frequency:1300000
/sys/kernel/debug/energy_model/pd1/cs:1300000/power:487
/sys/kernel/debug/energy_model/pd1/cs:1400000/cost:675 ...
$ grep . /sys/kernel/debug/energy_model/pd0/cs*/*
/sys/kernel/debug/energy_model/pd0/cs:1000000/cost:200
/sys/kernel/debug/energy_model/pd0/cs:1000000/frequency:1000000
/sys/kernel/debug/energy_model/pd0/cs:1000000/power:154
/sys/kernel/debug/energy_model/pd0/cs:1100000/cost:260
/sys/kernel/debug/energy_model/pd0/cs:1100000/frequency:1100000
/sys/kernel/debug/energy_model/pd0/cs:1100000/power:220
/sys/kernel/debug/energy_model/pd0/cs:1200000/cost:260
/sys/kernel/debug/energy_model/pd0/cs:1200000/frequency:1200000
/sys/kernel/debug/energy_model/pd0/cs:1200000/power:240
/sys/kernel/debug/energy_model/pd0/cs:1300000/cost:260
/sys/kernel/debug/energy_model/pd0/cs:1300000/frequency:1300000
/sys/kernel/debug/energy_model/pd0/cs:1300000/power:260
/sys/kernel/debug/energy_model/pd0/cs:200000/cost:130 ...
Please, do not describe entire Energy Model in commit message touching
DTS. It brings too much information which look unrelated and therefore
it makes difficult to spot real rationale behind the change. Just
mention:
1. Why you are doing it?
2. What are you doing?
3. How did you figure out magic constants here (details of "what")?
OK, I will clean this up.
To provide a proper value of the 'dynamic-power-coefficient' the real power
can be measured using a dedicated hardware, i.e. INA2xx. The Odroid-XU3
hwmon sensors have been used to capture the power value during a sysbench
test running on single core and at each possible OPP.
Since you mention the values, post them. That's the only thing which
reader cannot get on his own. All other values posted in commit
message will be seen after running tests...
Makes sense, but as you spotted it can vary probably due to ASV, so I
will skip to put values in commit message.
The measured values
were divided by 2, since the dynamic power is typically half of the
consumed power (the second half is static power). Next, the approximation
was made and the power model derived, showing the 'C' value of routhly X.
s/routhly/roughly/
What is X?
The 'X' is <128> or <310>
Check the example equations in drivers/opp/of.c [2].
Thus, i.e. the power = 1.0Watt at 1GHz => 0.5W dynamic power =>
dynamic-power-coefficient = 400
Using this simple technique we can provide and needed coefficient. The
s/and/the/ ?
correct
approximation does not have to be super precised. The proportion is
important and the difference between power consumed by different CPUs
running at the same frequency, which is then used in Energy Aware Scheduler
algorithms. An example power values on Odroid-XU3:
(LITTLE CPU)
/sys/kernel/debug/energy_model/pd0/cs:1000000/frequency:1000000
/sys/kernel/debug/energy_model/pd0/cs:1000000/power:154
For A7, 1V and 1 GHz this gives 142, not 154. Is it correct? What ASV
are you using?
Good question, it may vary depending on ASV. Would it vary also due to
bootloader?
This one is quite old:
U-Boot 2012.07 (Aug 11 2014 - 18:33:44) for Exynos5422
Odroid-xu3 rev0.2 20140529 ASV regs dump:
EXYNOS_CHIPID_REG_PKG_ID=0x320c832a
EXYNOS_CHIPID_REG_AUX_INFO=0x4f
Odroid-xu4 rev0.1 20180912 ASV regs dump:
EXYNOS_CHIPID_REG_PKG_ID=0x3b0e832a
EXYNOS_CHIPID_REG_AUX_INFO=0x100c004f
(big CPU)
/sys/kernel/debug/energy_model/pd1/cs:1000000/frequency:1000000
/sys/kernel/debug/energy_model/pd1/cs:1000000/power:310
In Odroid-XU3 case the derived coefficient value for 'big' CPU has:
dynamic-power-coefficient = <310>;
while the 'LITTLE':
dynamic-power-coefficient = <128>;
Make it all compact. First, you mention power values which are the
same as in the beginning of this commit message. Why repeating? Then
you mention the power coefficient in 4 lines instead of simple:
For Odroid XU3, the derived power coefficient is then 128 for an A7
CPU and 310 for an A15 CPU. Or something similar.
OK, I will keep simple, as you have commented.
[1] Documentation/devicetree/bindings/arm/cpus.yaml
[2] https://elixir.bootlin.com/linux/v5.4/source/drivers/opp/of.c#L1044
Refer to path inside, no external sources unless needed.
OK
Regards,
Lukasz
Best regards,
Krzysztof
