linux-kernel - Re: [PATCH v2] tools/power turbostat: Fix RAPL summary collection on AMD processors

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Date:   Tue, 20 Apr 2021 09:32:36 -0400
From:   Calvin Walton <calvin.walton@...stin.ca>
To:     Terry Bowman <terry.bowman@....com>, lenb@...nel.org,
        yu.c.chen@...el.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, bp@...e.de
Cc:     wei.huang2@....com
Subject: Re: [PATCH v2] tools/power turbostat: Fix RAPL summary collection
 on AMD processors

On Mon, 2021-04-19 at 14:58 -0500, Terry Bowman wrote:
> Turbostat fails to correctly collect and display RAPL summary
> information
> on Family 17h and 19h AMD processors. Running turbostat on these
> processors
> returns immediately. If turbostat is working correctly then RAPL
> summary
> data is displayed until the user provided command completes. If a
> command
> is not provided by the user then turbostat is designed to
> continuously
> display RAPL information until interrupted.
> 
> The issue is due to offset_to_idx() and idx_to_offset() missing
> support for
> AMD MSR addresses/offsets. offset_to_idx()'s switch statement is
> missing
> cases for AMD MSRs and idx_to_offset() does not include a path to
> return
> AMD MSR(s) for any idx.

Ah, when I was looking at Boris's patch, it lead me to one more spot
that was missed with the off_t type - inside the function
update_msr_sum(), the offset is also stored in a variable of type int,
and as a result the background update for AMD's MSR when turbostat is
used with long durations won't work. (It's skipped because of the
offset < 0 check).

-- 
Calvin Walton <calvin.walton@...stin.ca>