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

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Date:   Fri, 31 Jan 2020 14:30:13 +0100
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     lukasz.luba@....com
Cc:     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,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        cw00.choi@...sung.com, robh+dt@...nel.org, mark.rutland@....com,
        dietmar.eggemann@....com
Subject: Re: [PATCH 3/3] ARM: exynos_defconfig: Enable Energy Model
 framework


Hi,

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

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"?

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

> 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