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tetumetal
n00b
Joined: 09 Jun 2022
Posts: 15
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 Posted: Fri Sep 16, 2022 8:29 pm Post subject: zen 2 and acpitool CPU frequency |
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hi Gentoo people,
I have a mini pc with a ryzen 4800U CPU, and the CPU frequency seems to be all the time at maximum (above 4 GHz).
When I check the current cpu frequency with acpitool, I get this output:
| Code: |
acpitool -c
CPU type : AMD Ryzen 7 4800U with Radeon Graphics
Min/Max frequency : 1400/1800 MHz
Current frequency : 4141 MHz
Frequency governor : schedutil
Freq. scaling driver : acpi-cpufreq
Cache size : 1400.000 KB
Bogomips : 3594.68
Bogomips : 3594.68
Bogomips : 3594.68
Bogomips : 3594.68
Bogomips : 3594.68
Bogomips : 3594.68
Bogomips : 3594.68
Bogomips : 3594.68
Function Show_CPU_Info : could not read directory /proc/acpi/processor/
Make sure your kernel has ACPI processor support enabled.
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When, I check the same with cpupower, I get this:
| Code: |
cpupower frequency-info
analyzing CPU 0:
driver: acpi-cpufreq
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: Cannot determine or is not supported.
hardware limits: 1.40 GHz - 1.80 GHz
available frequency steps: 1.80 GHz, 1.70 GHz, 1.40 GHz
available cpufreq governors: conservative ondemand userspace powersave performance schedutil
current policy: frequency should be within 1.40 GHz and 1.80 GHz.
The governor "schedutil" may decide which speed to use
within this range.
current CPU frequency: 1.40 GHz (asserted by call to hardware)
boost state support:
Supported: yes
Active: yes
Boost States: 0
Total States: 3
Pstate-P0: 1800MHz
Pstate-P1: 1700MHz
Pstate-P2: 1400MHz
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And, when I monitor the power with cpupower, I get this:
| Code: |
cpupower monitor
WARNING: at least one cpu is offline
| Mperf || Idle_Stats
CPU| C0 | Cx | Freq || POLL | C1 | C2 | C3
0| 1.37| 98.63| 4132|| 0.00| 1.01| 0.00| 97.78
2| 1.48| 98.52| 4133|| 0.00| 0.98| 0.02| 97.74
4| 0.52| 99.48| 4148|| 0.00| 0.96| 0.00| 98.60
6| 0.82| 99.18| 4132|| 0.00| 0.41| 0.00| 98.89
8| 0.23| 99.77| 4135|| 0.00| 0.00| 0.15| 99.67
10| 0.48| 99.52| 4143|| 0.00| 0.00| 0.25| 99.37
12| 0.01| 99.99| 4165|| 0.00| 0.00| 0.00| 99.99
14| 0.74| 99.26| 4144|| 0.02| 3.81| 0.25| 95.31
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Another funny behavior that I observed is that when I start up the computer, the frequency is ~1.8 GHz. But, if there's something that triggers the frequency increase (like extra cpu load), the frequency will stay high (say ~4 GHz) forever after next reboot. This happens regardless if the average load goes back to ~0% for several tens of minutes.
Honestly, I don't believe that the CPU is all the timing running at ~4 GHz, since I montior a Tctl of 66C, which is rather low.
Is this CPU freq. of ~4 GHz correct? Or is acpitool misreading it?
Thanks! |
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tetumetal
n00b
Joined: 09 Jun 2022
Posts: 15
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| Posted: Mon Sep 19, 2022 11:51 am Post subject: Re: zen 2 and acpitool CPU frequency |
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I found the problem: basically, the cpu boost is active from boot and the linux kernel does not automatically control its activation. Therefore, after booting, the cpu is running at a very high clock speed regardless of the cpu load, which is pretty bad. Also, I could not find any user space application that can automatically control the boost activation.
So, I wrote a simple script to manually enable/disable the frequency boost, which effectively writes the file:
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/sys/devices/system/cpu/cpufreq/boost
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