linux-kernel - Re: [PATCH] tools/power turbostat: Fix Bzy

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Date:   Mon, 27 Nov 2023 20:39:57 -0500
From:   Len Brown <lenb@...nel.org>
To:     Doug Smythies <dsmythies@...us.net>
Cc:     Peng Liu <pngliu@...mail.com>, Wyes Karny <wyes.karny@....com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        liupeng17@...ovo.com
Subject: Re: [PATCH] tools/power turbostat: Fix Bzy_MHz calculation equation

Peng Liu,
Thanks for the close read of the documentation, and the patch.
I've applied it, though I re-wrote the commit message (below) to make
it clear it is a documentation fix, as the code was already correct.

thanks,
-Len

ps. I would have replied to your original e-mail, but there was a
period where gmail dropped mail due to space limitations.
No worries, as Doug said, everything is in patchwork.


    tools/power turbostat: Fix Bzy_MHz documentation typo

    The code calculates Bzy_MHz by multiplying TSC_delta *
APERF_delta/MPERF_delta
    The man page erroneously showed that TSC_delta was divided.

On Thu, Nov 2, 2023 at 11:31 AM Doug Smythies <dsmythies@...us.net> wrote:
>
> Hi Peng and Wyes,
>
> Just for your information about your recent "ping"s about your turbostat patches:
>
> Please be aware that there is rarely any reply. There tends to be about 2 turbostat updates released per year. Your patches are in patchworks [1], as are some others, including an old one of mine from 2023.04.03
> Eventually there will be an update, and hopefully it will include all our patches.
>
> [1] https://patchwork.kernel.org/project/linux-pm/list/?series=&submitter=&state=&q=&archive=&delegate=107
>
> ... Doug
>
> On 2023.10.29 08:12 Peng Liu wrote:
>
> > Ping
> >
> > On 2023/10/7 13:46, Peng Liu wrote:
> >> From: Peng Liu <liupeng17@...ovo.com>
> >>
> >> To calculate Bzy_MHz, TSC_delta should multiply APERF_delta instead
> >> of dividing it.
> >>
> >> Signed-off-by: Peng Liu <liupeng17@...ovo.com>
> >> ---
> >>   tools/power/x86/turbostat/turbostat.8 | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/tools/power/x86/turbostat/turbostat.8 b/tools/power/x86/turbostat/turbostat.8
> >> index 8f08c3fd498d..1ba6340d3b3d 100644
> >> --- a/tools/power/x86/turbostat/turbostat.8
> >> +++ b/tools/power/x86/turbostat/turbostat.8
> >> @@ -370,7 +370,7 @@ below the processor's base frequency.
> >>
> >>   Busy% = MPERF_delta/TSC_delta
> >>
> >> -Bzy_MHz = TSC_delta/APERF_delta/MPERF_delta/measurement_interval
> >> +Bzy_MHz = TSC_delta*APERF_delta/MPERF_delta/measurement_interval
> >>
> >>   Note that these calculations depend on TSC_delta, so they
> >>   are not reliable during intervals when TSC_MHz is not running at the base frequency.
>


-- 
Len Brown, Intel