linux-kernel - problem in changing from active to passive mode

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Date:   Sun, 24 Oct 2021 15:02:58 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org
cc:     linux-kernel@...r.kernel.org
Subject: problem in changing from active to passive mode

Hello,

I have an Intel 6130 and an Intel 5218.  These machines have HWP.  They
are configured to boot with active mode and performance as the power
governor.  Since the following commit:

commit a365ab6b9dfbaf8fb4fb4cd5d8a4c55dc4fb8b1c (HEAD, refs/bisect/bad)
Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Date:   Mon Dec 14 21:09:26 2020 +0100

    cpufreq: intel_pstate: Implement the ->adjust_perf() callback

If I change te mode from active to passive, I have the impression that the
machine is no longer able to raise the core frequencies above the minimum.
Changing the mode back to active has no effect.  This persists if I reboot
to another kernel.

Here are some runs that illustrate the problem.  I have tested the
benchmark many times, and apart from this issue its performance is stable.

Intel 6130:

root@...i-2:/tmp# java -jar dacapo-9.12-MR1-bach.jar avrora -n 3
===== DaCapo 9.12-MR1 avrora starting warmup 1 =====
===== DaCapo 9.12-MR1 avrora completed warmup 1 in 3420 msec =====
===== DaCapo 9.12-MR1 avrora starting warmup 2 =====
===== DaCapo 9.12-MR1 avrora completed warmup 2 in 2536 msec =====
===== DaCapo 9.12-MR1 avrora starting =====
===== DaCapo 9.12-MR1 avrora PASSED in 2502 msec =====
root@...i-2:/tmp# echo passive | tee /sys/devices/system/cpu/intel_pstate/status
passive
root@...i-2:/tmp#
root@...i-2:/tmp# echo active | tee /sys/devices/system/cpu/intel_pstate/status
active
root@...i-2:/tmp# java -jar dacapo-9.12-MR1-bach.jar avrora -n 3
===== DaCapo 9.12-MR1 avrora starting warmup 1 =====
===== DaCapo 9.12-MR1 avrora completed warmup 1 in 7561 msec =====
===== DaCapo 9.12-MR1 avrora starting warmup 2 =====
===== DaCapo 9.12-MR1 avrora completed warmup 2 in 6528 msec =====
===== DaCapo 9.12-MR1 avrora starting =====
===== DaCapo 9.12-MR1 avrora PASSED in 7796 msec =====

-------------------------------------------------------------------------

Intel 5218:

root@...ll-2:/tmp# java -jar dacapo-9.12-MR1-bach.jar avrora -n 3
===== DaCapo 9.12-MR1 avrora starting warmup 1 =====
===== DaCapo 9.12-MR1 avrora completed warmup 1 in 2265 msec =====
===== DaCapo 9.12-MR1 avrora starting warmup 2 =====
===== DaCapo 9.12-MR1 avrora completed warmup 2 in 2033 msec =====
===== DaCapo 9.12-MR1 avrora starting =====
===== DaCapo 9.12-MR1 avrora PASSED in 2068 msec =====
root@...ll-2:/tmp# echo passive | tee /sys/devices/system/cpu/intel_pstate/status
passive
root@...ll-2:/tmp# echo active | tee /sys/devices/system/cpu/intel_pstate/statusactive
root@...ll-2:/tmp# java -jar dacapo-9.12-MR1-bach.jar avrora -n 3
===== DaCapo 9.12-MR1 avrora starting warmup 1 =====
===== DaCapo 9.12-MR1 avrora completed warmup 1 in 4363 msec =====
===== DaCapo 9.12-MR1 avrora starting warmup 2 =====
===== DaCapo 9.12-MR1 avrora completed warmup 2 in 4486 msec =====
===== DaCapo 9.12-MR1 avrora starting =====
===== DaCapo 9.12-MR1 avrora PASSED in 3417 msec =====

-------------------------------------------------------------------------

thanks,
julia