Re: [PATCH 3/3] ARM: exynos_defconfig: Enable Energy Model framework

[Bartlomiej Zolnierkiewicz]

On 1/31/20 2:47 PM, Bartlomiej Zolnierkiewicz wrote:
> 
> On 1/31/20 2:31 PM, Krzysztof Kozlowski wrote:
>> On Fri, 31 Jan 2020 at 14:30, Bartlomiej Zolnierkiewicz
>> <b.zolnierkie@xxxxxxxxxxx> wrote:
>>>
>>>
>>> Hi,
>>>
>>> On 1/27/20 10:54 PM, lukasz.luba@xxxxxxx wrote:
>>>> From: Lukasz Luba <lukasz.luba@xxxxxxx>
>>>>
>>>> Enable the Energy Model (EM) brings possibility to use Energy Aware
>>>> Scheduler (EAS). This compiles the EM but does not enable to run EAS in
>>>> default. The EAS only works with SchedUtil - a CPUFreq governor which
>>>> handles direct requests from the scheduler for the frequency change. Thus,
>>>> to make EAS working in default, the SchedUtil governor should be
>>>> configured as default CPUFreq governor. Although, the EAS might be enabled
>>>> in runtime, when the EM is present for CPUs, the SchedUtil is compiled and
>>>> then set as CPUFreq governor, i.e.:
>>>>
>>>> echo schedutil > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
>>>> echo schedutil > /sys/devices/system/cpu/cpu4/cpufreq/scaling_governor
>>>>
>>>> To check if EAS is ready to work, the read output from the command below
>>>> should show '1':
>>>> cat /proc/sys/kernel/sched_energy_aware
>>>>
>>>> To disable EAS in runtime simply 'echo 0' to the file above.
>>>>
>>>> Some test results, which stress the scheduler on Odroid-XU3:
>>>> hackbench -l 500 -s 4096
>>>> With mainline code and with this patch set.
>>>>
>>>> The tests have been made with and without CONFIG_PROVE_LOCKING (PL)
>>>> (which is set to =y in default exynos_defconfig)
>>>>
>>>>               |               this patch set                  | mainline
>>>>               |-----------------------------------------------|---------------
>>>>               | performance   | SchedUtil     | SchedUtil     | performance
>>>>               | governor      | governor      | governor      | governor
>>>>               |               | w/o EAS       | w/ EAS        |
>>>> ----------------|---------------|---------------|---------------|---------------
>>>> hackbench w/ PL | 12.7s               | 11.7s         | 12.0s         | 13.0s - 12.2s
>>>> hackbench w/o PL| 9.2s                | 8.1s          | 8.2s          | 9.2s - 8.4s
>>>
>>> Would you happen to have measurements of how much power is
>>> saved by running hackbench using "SchedUtil governor w/ EAS"
>>> instead of "SchedUtil governor w/o EAS"?
>>
>> That's a good point and quite important reason behind enabling (or not) EAS...
> 
> IIUC EAS is enabled by default if you use SchedUtil
> governor and Energy Model is available on you platform.
> 
> [ SchedUtil governor is enabled in exynos_defconfig
>   although not enabled by default currently. ]

s/enabled/used/

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics