linux-kernel - Re: [PATCH 4/4] arm64: dts: rockchip: Add OPP data for CPU cores on RK3588

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Date: Mon, 29 Jan 2024 08:39:11 +0100
From: Dragan Simic <dsimic@...jaro.org>
To: Alexey Charkov <alchark@...il.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>, Rob Herring
 <robh+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
 Heiko Stuebner <heiko@...ech.de>, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH 4/4] arm64: dts: rockchip: Add OPP data for CPU cores on
 RK3588

Hello Alexey,

On 2024-01-29 01:09, Dragan Simic wrote:
> On 2024-01-28 20:14, Alexey Charkov wrote:
>> On Sun, Jan 28, 2024 at 7:35 AM Dragan Simic <dsimic@...jaro.org> 
>> wrote:
>>> Just checking, running the test on just two CPU cores was enough to
>>> keep the package temperature at around 80 oC?
>> 
>> No, not even remotely.
>> 
>> I kept the continuous 6 dhrystone threads running on all the other
>> cores (`taskset -c 0-5 ./dhrystone -t 6 -r 6000`) to let it reach the
>> throttling temperature. This adds further imprecision to the benchmark
>> of course, because the governor might choose to throttle some of the
>> cores that do not participate in the timed benchmarking run, and thus
>> lend some thermal headroom to the latter. That didn't seem to happen
>> from my naked-eye observation via `watch "cpupower -c 0,4,6
>> frequency-info | grep current"`, although I admit that I didn't record
>> more granular logs of frequency states, and some quick transitions to
>> lower frequencies could also have happened on the other cores. Don't
>> think it's a major influence though, because a quick transition back
>> and forth shouldn't have contributed much to the thermal output.
> 
> Thank you for the clarification!
> 
> You're right, that might have introduced some inaccuracy into the test
> results, and it also made the tests kind of hardly repeatable.  On the
> other hand, that way the synthetic CPU test feels a bit more like some
> real-world CPU load, in which multiple resource-hungry tasks usually
> compete for the CPU cores and the thermal budget.
> 
> Though, as we know repeatability is the key for a scientific approach,
> but it also usually contradicts with simulating real-world loads that
> are of rather random nature.  Well, testing is hard. :)
> 
> I'll think a bit more about all this, and I'll come back with an 
> update.
> Maybe I'll also be able to join the testing.

Good news! :)  Thanks to Radxa, I'll be able to do the testing on my
side, perhaps in about a week or two.  If you agree, it might be the 
best
to wait for those test results as well;  of course, I'll keep thinking
about some kind of a test suite in the meantime, which we should be able
to use on other boards as well.