linux-kernel - Re: [PATCH v3 0/5] Refactor thermal pressure update to avoid code duplication

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Message-ID: <2c54dbbd-2ecb-fb76-fa9f-9752f429c20e@linaro.org>
Date:   Mon, 8 Nov 2021 16:31:44 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Steev Klimaszewski <steev@...i.org>,
        Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, sudeep.holla@....com,
        will@...nel.org, catalin.marinas@....com, linux@...linux.org.uk,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        viresh.kumar@...aro.org, amitk@...nel.org,
        daniel.lezcano@...aro.org, amit.kachhap@...il.com,
        bjorn.andersson@...aro.org, agross@...nel.org
Subject: Re: [PATCH v3 0/5] Refactor thermal pressure update to avoid code
 duplication



On 11/8/21 10:22 AM, Steev Klimaszewski wrote:
> 
>> Hi Steev,
>>
>> So this depends on the cpufreq governor you are using. By-default arm 
>> systems have sched-util governor enabled. This means you will scale up 
>> to boost depending on cpu load and not always. If you want to ensure 
>> you are always hitting boost frequency, you should enable performance 
>> governor for cpufreq and try.
>>
>> Also since the defconfig has by default CPU_FREQ_STAT enabled, you 
>> should be able to get statistics out of cpufreq to see the time spent 
>> by a cpu in each frequency. I think cpufreq-info -s should give you 
>> this info. If not, you can explicitly get it for each cpu from
>>
>> cat /sys/devices/system/cpu/cpu<X>/cpufreq/stats/time_in_state
>>
>> Regarding temperature, if you have applied all the patches in the 
>> sdm845 LMh series and have LMh enabled, cpu throttling starts around 
>> 95 degree C.
>>
> Hi Thara,
> 
> Indeed, I ended up finding the time_in_state when I was doing more 
> digging after my last mail.  I do have the sdm845 LMh series and LMh 
> enabled, however I don't think I've ever seen my system go above 90C here.
> 
> So a quick look, and... we are simply almost never getting the 2.95GHz 
> at all, regardless of workload.  I saw Lukasz response as well about the 
> math possibly being wrong, but I haven't had a chance.
> 
> Regarding the time in state - I went with policy4 instead of per cpu 
> (for brevity sake) and it's here:
> 
> c630:~$ cat /sys/devices/system/cpu/cpufreq/policy4/stats/time_in_state
> 825600 225037
> 902400 92
> 979200 205
> 1056000 96
> 1209600 902
> 1286400 386
> 1363200 396
> 1459200 217
> 1536000 101
> 1612800 75
> 1689600 95
> 1766400 130
> 1843200 255
> 1920000 318
> 1996800 92
> 2092800 87
> 2169600 66
> 2246400 60
> 2323200 58
> 2400000 54
> 2476800 47
> 2553600 50
> 2649600 69
> 2745600 58
> 2841600 54619
> 2956800 5
> 
> So we spend *very* little time in 2.96GHz and this is after almost 14 
> hours of uptime on the C630.  By comparison, on a Pinebook Pro where 
> I've added in 2GHz as a boost frequency :

Hi Steev,

IIUC, PineBook Pro has Rockchip RK3399 which has 2 Cortex A-72 and 4 
Cortex A-52 where as C630 has Qualcomm sdm845 which has 4 Cortex A-75 
and 4 Cortex A-55. Task placements and subsequently cpu load will be 
different for both the platforms. With the same workload, I will expect 
Rockchip to system to be more loaded than sdm845. Having said that, what 
cpu-freq governor are you using on both the systems.


> 
> pinebook-pro:~$ cat 
> /sys/devices/system/cpu/cpufreq/policy4/stats/time_in_state
> 408000 16084466
> 600000 27212
> 816000 32487
> 1008000 11331
> 1200000 13268
> 1416000 75078
> 1608000 18392
> 1800000 207266
> 2016000 648612
> 
> With the Pinebook Pro, which doesn't even come close to getting to 95C, 
> we spend a lot more time in 2GHz.
> 
> -- steev
> 

-- 
Warm Regards
Thara (She/Her/Hers)