On 1/31/20 2:31 PM, Krzysztof Kozlowski wrote:

On Fri, 31 Jan 2020 at 14:30, Bartlomiej Zolnierkiewicz
[off-list ref] wrote:

quoted

Hi,

On 1/27/20 10:54 PM, lukasz.luba@arm.com wrote:

quoted

From: Lukasz Luba <lukasz.luba@arm.com>

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. ]

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

Best regards,
Krzysztof

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