linux-kernel - [PATCH 3/3] ARM: exynos_defconfig: Enable Energy Model framework

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Message-Id: <20200127215453.15144-4-lukasz.luba@arm.com>
Date:   Mon, 27 Jan 2020 21:54:53 +0000
From:   lukasz.luba@....com
To:     kgene@...nel.org, krzk@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org
Cc:     myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        cw00.choi@...sung.com, robh+dt@...nel.org, mark.rutland@....com,
        b.zolnierkie@...sung.com, lukasz.luba@....com,
        dietmar.eggemann@....com
Subject: [PATCH 3/3] ARM: exynos_defconfig: Enable Energy Model framework

From: Lukasz Luba <lukasz.luba@....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

Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
 arch/arm/configs/exynos_defconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/configs/exynos_defconfig b/arch/arm/configs/exynos_defconfig
index 1db857056992..c0f8ecabc607 100644
--- a/arch/arm/configs/exynos_defconfig
+++ b/arch/arm/configs/exynos_defconfig
@@ -18,6 +18,7 @@ CONFIG_ZBOOT_ROM_BSS=0x0
 CONFIG_ARM_APPENDED_DTB=y
 CONFIG_ARM_ATAG_DTB_COMPAT=y
 CONFIG_CMDLINE="root=/dev/ram0 rw ramdisk=8192 initrd=0x41000000,8M console=ttySAC1,115200 init=/linuxrc mem=256M"
+CONFIG_ENERGY_MODEL=y
 CONFIG_CPU_FREQ=y
 CONFIG_CPU_FREQ_STAT=y
 CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y
-- 
2.17.1