linux-kernel - Re: [RFC 2/2] selftest/cpuidle: Add support for cpuidle latency measurement

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Message-ID: <CAAYoRsW-E_Rek-c=e3xr8dTNUWud1AkndNaNySCZpt=h1qSf7g@mail.gmail.com>
Date:   Wed, 17 Mar 2021 14:00:57 -0700
From:   Doug Smythies <dsmythies@...us.net>
To:     Pratik Rajesh Sampat <psampat@...ux.ibm.com>
Cc:     rjw@...ysocki.net, Daniel Lezcano <daniel.lezcano@...aro.org>,
        shuah@...nel.org, ego@...ux.vnet.ibm.com, svaidy@...ux.ibm.com,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org, pratik.r.sampat@...il.com,
        dsmythies <dsmythies@...us.net>
Subject: Re: [RFC 2/2] selftest/cpuidle: Add support for cpuidle latency measurement

Hi Pratik,

It just so happens that I have been trying Artem's version this last
week, so I tried yours.

On Mon, Mar 15, 2021 at 4:49 AM Pratik Rajesh Sampat
<psampat@...ux.ibm.com> wrote:
>
...
> To run this test specifically:
> $ make -C tools/testing/selftests TARGETS="cpuidle" run_tests

While I suppose it should have been obvious, I interpreted
the "$" sign to mean I could run as a regular user, which I can not.

> There are a few optinal arguments too that the script can take
>         [-h <help>]
>         [-m <location of the module>]
>         [-o <location of the output>]
>         [-v <verbose> (run on all cpus)]
> Default Output location in: tools/testing/cpuidle/cpuidle.log

Isn't it:

tools/testing/selftests/cpuidle/cpuidle.log

? At least, that is where my file was.

Other notes:

No idle state for CPU 0 ever gets disabled.
I assume this is because CPU 0 can never be offline,
so that bit of code (Disable all stop states) doesn't find its state.
By the way, processor = Intel i5-9600K

The system is left with all idle states disabled, well not for CPU 0
as per the above comment. The suggestion is to restore them,
otherwise my processor hogs 42 watts instead of 2.

My results are highly variable per test.
My system is very idle:
Example (from turbostat at 6 seconds sample rate):
Busy%   Bzy_MHz IRQ     PkgTmp  PkgWatt RAMWatt
0.03    4600    153     28      2.03    1.89
0.01    4600    103     29      2.03    1.89
0.05    4600    115     29      2.08    1.89
0.01    4600    95      28      2.09    1.89
0.03    4600    114     28      2.11    1.89
0.01    4600    107     29      2.07    1.89
0.02    4600    102     29      2.11    1.89

...

... Doug