Re: problem in changing from active to passive mode

On Sun, Oct 24, 2021 at 6:03 AM Julia Lawall [off-list ref] wrote:

Hello,

Hi,

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 [off-list ref]
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.

Could you also list the CPU frequency scaling governor being used in your
tests. I know you mentioned the performance governor above, but it
changes between active/passive/active transitions.

Example from my test computer:

Note 1: It is only for brevity of this e-mail that I only list for one CPU.
Obviously, I looked at all CPUs when doing this.

Note 2: The test example and conditions have been cherry picked
for dramatic effect.

$ cat /sys/devices/system/cpu/cpu6/cpufreq/scaling_driver
intel_pstate
$ cat /sys/devices/system/cpu/cpu6/cpufreq/scaling_governor
performance
$ cat /sys/devices/system/cpu/intel_pstate/status
active
$ ./ping-pong-many 100000 500 10
1418.0660 usecs/loop. (less is better)

$ echo passive | sudo tee /sys/devices/system/cpu/intel_pstate/status
passive
$ cat /sys/devices/system/cpu/cpu6/cpufreq/scaling_driver
intel_cpufreq
$ cat /sys/devices/system/cpu/cpu6/cpufreq/scaling_governor
schedutil
$ cat /sys/devices/system/cpu/intel_pstate/status
passive
$ ./ping-pong-many 100000 500 10
5053.6355 usecs/loop.

$ echo active | sudo tee /sys/devices/system/cpu/intel_pstate/status
active
$ cat /sys/devices/system/cpu/cpu6/cpufreq/scaling_driver
intel_pstate
$ cat /sys/devices/system/cpu/cpu6/cpufreq/scaling_governor
powersave
$ cat /sys/devices/system/cpu/intel_pstate/status
active
$ ./ping-pong-many 100000 500 10
2253.5833 usecs/loop.

... Doug

Intel 6130:

root@yeti-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@yeti-2:/tmp# echo passive | tee /sys/devices/system/cpu/intel_pstate/status
passive
root@yeti-2:/tmp#
root@yeti-2:/tmp# echo active | tee /sys/devices/system/cpu/intel_pstate/status
active
root@yeti-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@troll-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@troll-2:/tmp# echo passive | tee /sys/devices/system/cpu/intel_pstate/status
passive
root@troll-2:/tmp# echo active | tee /sys/devices/system/cpu/intel_pstate/statusactive
root@troll-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