AMD P-State Support Coming For The CPUPower Tool

[phoronix]

Phoronix: AMD P-State Support Coming For The CPUPower Tool

With the forthcoming Linux 5.17 kernel there is the new AMD P-State driver aiming to provide better power efficiency than the ACPI CPUFreq driver that has long been used on AMD platforms. For complementing that AMD P-State driver, AMD has also been working on adding their CPU P-State support to Linux's cpupower tool...

https://www.phoronix.com/scan.php?page=news_item&px=CPUPower-AMD-P-State

[HD7950]

Currently amd_pstate is not working well on zen2 and zen3 CPU's except Cezzane. I have a lot of slowdowns when i am playing emulators or steam games using any cpu governor other than performance.

More info here: https://www.kernel.org/doc/html/late...for-amd-pstate

[skeevy420]

Currently amd_pstate is not working well on zen2 and zen3 CPU's except Cezzane. I have a lot of slowdowns when i am playing emulators or steam games using any cpu governor other than performance.

More info here: https://www.kernel.org/doc/html/late...for-amd-pstate

Try setting "clocksource=tsc tsc=reliable" in your kernel command line (that's probably overkill; only tsc=reliable should be necessary). Enabling C-States can make tsc have an issue (forgot the link) so the kernel switches the clocksource to hpet and hpet can have horrible gaming results. I'm wondering if that's what's happening here.

I'm also using cfs and a tkg-patched ondemand. You can get close enough to that with cfs-zen-tweaks or a linux-zen kernel.

That's my basic setup and amd_pstate works just fine.

[HD7950]

Try setting "clocksource=tsc tsc=reliable" in your kernel command line (that's probably overkill; only tsc=reliable should be necessary). Enabling C-States can make tsc have an issue (forgot the link) so the kernel switches the clocksource to hpet and hpet can have horrible gaming results. I'm wondering if that's what's happening here.

I'm also using cfs and a tkg-patched ondemand. You can get close enough to that with cfs-zen-tweaks or a linux-zen kernel.

That's my basic setup and amd_pstate works just fine.

# cat /sys/devices/system/clocksource/clocksource*/current_clocksource
tsc

This does not seem to be my case.

Can you post your cpupower frequency-info?

# cpupower frequency-info
analyzing CPU 0:
 driver: amd-pstate
 CPUs which run at the same hardware frequency: 0
 CPUs which need to have their frequency coordinated by software: 0
 maximum transition latency: 131 us
 hardware limits: 550 MHz - 4.43 GHz
 available cpufreq governors: ondemand powersave performance schedutil
 current policy: frequency should be within 550 MHz and 4.43 GHz.
                 The governor "schedutil" may decide which speed to use
                 within this range.
 current CPU frequency: Unable to call hardware
 current CPU frequency: 4.04 GHz (asserted by call to kernel)
 boost state support:
   Supported: yes
   Active: yes
   Boost States: 0
   Total States: 3
   Pstate-P0:  3600MHz
   Pstate-P1:  2800MHz
   Pstate-P2:  2200MHz

[skeevy420]

This is with the v7 patches; w/o these cpupower patches. I'll try these out later on today.

cpupower frequency-info
analyzing CPU 0:
 driver: amd-pstate
 CPUs which run at the same hardware frequency: 0
 CPUs which need to have their frequency coordinated by software: 0
 maximum transition latency: 131 us
 hardware limits: 400 MHz - 4.31 GHz
 available cpufreq governors: conservative ondemand userspace powersave performance schedutil
 current policy: frequency should be within 400 MHz and 4.31 GHz.
                 The governor "ondemand" may decide which speed to use
                 within this range.
 current CPU frequency: Unable to call hardware
 current CPU frequency: 3.69 GHz (asserted by call to kernel)
 boost state support:
   Supported: yes
   Active: no

[HD7950]

This is with the v7 patches; w/o these cpupower patches. I'll try these out later on today.

cpupower frequency-info
analyzing CPU 0:
driver: amd-pstate
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 131 us
hardware limits: 400 MHz - 4.31 GHz
available cpufreq governors: conservative ondemand userspace powersave performance schedutil
current policy: frequency should be within 400 MHz and 4.31 GHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency: Unable to call hardware
current CPU frequency: 3.69 GHz (asserted by call to kernel)
boost state support:
Supported: yes
Active: no

Run it as root.

[perpetually high]

HD7950

Here's mine if you need. Getting different readouts on 5.17-rc4 vs 5.16.10. Both custom kernels.

5.16.10:

# cpupower frequency-info
analyzing CPU 0:
driver: amd-pstate
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 131 us
hardware limits: 550 MHz - 4.93 GHz
available cpufreq governors: conservative ondemand userspace powersave performance schedutil
current policy: frequency should be within 550 MHz and 4.93 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency: Unable to call hardware
current CPU frequency: 3.61 GHz (asserted by call to kernel)
boost state support:
Supported: yes
Active: yes
AMD PSTATE Highest Performance: 166. Maximum Frequency: 4.93 GHz.
AMD PSTATE Nominal Performance: 128. Nominal Frequency: 3.80 GHz.
AMD PSTATE Lowest Non-linear Performance: 59. Lowest Non-linear Frequency: 1.75 GHz.
AMD PSTATE Lowest Performance: 19. Lowest Frequency: 550 MHz.

5.17-rc4:

# cpupower frequency-info
analyzing CPU 0:
driver: amd-pstate
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 131 us
hardware limits: 550 MHz - 4.93 GHz
available cpufreq governors: conservative ondemand userspace powersave performance schedutil
current policy: frequency should be within 550 MHz and 4.93 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency: Unable to call hardware
current CPU frequency: 3.76 GHz (asserted by call to kernel)
boost state support:
Supported: yes
Active: yes
Boost States: 0
Total States: 3
Pstate-P0: 3800MHz
Pstate-P1: 2800MHz
Pstate-P2: 2200MHz

[yump]

perpetually high

current policy: frequency should be within 550 MHz and 4.93 GHz.

Lowest Non-linear Performance: 59. Lowest Non-linear Frequency: 1.75 GHz.

If I recall and understand correctly what AMD employees have posted on the mailing list, that means there is no perf/watt gain for any frequency below 1.75 GHz, and therefore no reason to use them unless your CPU is overheating. So for best battery life from race-to-idle, you probably want to:

# cpupower frequency-set -d 1.75GHz