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#26 2022-08-04 09:58:27

graysky
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From: :wq
Registered: 2008-12-01
Posts: 10,419
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Re: using the amd-pstate driver in kernel 5.17

The TODO comment is still present in the driver code.  Even though it scales, it is likely giving you inferior performance.

https://github.com/torvalds/linux/blob/ … tate.c#L53


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#27 2022-08-04 11:00:31

regulator
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Registered: 2020-01-15
Posts: 15

Re: using the amd-pstate driver in kernel 5.17

graysky wrote:

The TODO comment is still present in the driver code.  Even though it scales, it is likely giving you inferior performance.

https://github.com/torvalds/linux/blob/ … tate.c#L53

good callout, it's definitely still in the early stages.. I'll run some power usage benchmarks when I get time to see if its actually performing better or not.

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#28 2022-08-04 11:15:22

agapito
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From: Spain
Registered: 2008-11-13
Posts: 551

Re: using the amd-pstate driver in kernel 5.17

regulator wrote:

Good to hear, I found out that it's working properly on my system (5.18 kernel still) except when using schedutil which doesn't go lower than 2500mhz, all the other governors obey the ranges either preset or set by me. I saw a bug report open which I believe relates to the issue so assume it will get resolved in a later kernel.

I haven't done any formal testing but it seems that using conservative for example, the battery will last longer overall.

I'm using schedutil and like i said before, my Zen3 CPU can idle at 550 Mhz. Are u running your latest bios available for your motherboard?

graysky wrote:

The TODO comment is still present in the driver code.  Even though it scales, it is likely giving you inferior performance.

https://github.com/torvalds/linux/blob/ … tate.c#L53

What I can say is I don´t have any slowdown or stuttering like the last time i tried it (5.17)


Excuse my poor English.

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#29 2022-08-12 22:21:58

I_Use_Arch_BTW45
Member
Registered: 2021-12-05
Posts: 42

Re: using the amd-pstate driver in kernel 5.17

when I type lscpu, it shows that cppc is supported, but when I run sudo modprobe amd_pstate dyndbg==pmf -v
I get
amd_pstate:amd_pstate_init: amd_pstate: the _CPC object is not present in SBIOS

I am using a ideapad flex 5 with a ryzen 7 4700u
there is no option in my bios to enable cppc, nor is there any info online or in the bios stating that the laptop doesn't support it

Last edited by I_Use_Arch_BTW45 (2022-08-12 22:24:51)

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#30 2022-08-13 04:39:57

regulator
Member
Registered: 2020-01-15
Posts: 15

Re: using the amd-pstate driver in kernel 5.17

I_Use_Arch_BTW45 wrote:

when I run sudo modprobe amd_pstate dyndbg==pmf -v
I get
amd_pstate:amd_pstate_init: amd_pstate: the _CPC object is not present in SBIOS

Did you already add those two kernel parameters?
I have an Ideapad and I believe CPPC is already enabled, there is no toggle in my BIOS.

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#31 2022-08-15 11:01:49

graysky
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Posts: 10,419
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Re: using the amd-pstate driver in kernel 5.17

https://www.phoronix.com/news/AMD-P-Sta … t-Miss-6.0  but the v5 proposed changes still include the TODO statement for share memory chips


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#32 2022-08-15 15:45:11

agapito
Member
From: Spain
Registered: 2008-11-13
Posts: 551

Re: using the amd-pstate driver in kernel 5.17

graysky wrote:

https://www.phoronix.com/news/AMD-P-Sta … t-Miss-6.0  but the v5 proposed changes still include the TODO statement for share memory chips

I applied the new patch against 5.19.1 and my Zen3 system just works fine. I don´t even compile apci-cpufreq module on my personal kernel.


Excuse my poor English.

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#33 2022-08-15 15:55:21

graysky
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From: :wq
Registered: 2008-12-01
Posts: 10,419
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Re: using the amd-pstate driver in kernel 5.17

Assuming you are force enabling the driver, it may work fine but it is likely not optimal.  See the comments in the code I linked above.


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#34 2022-08-15 17:01:57

agapito
Member
From: Spain
Registered: 2008-11-13
Posts: 551

Re: using the amd-pstate driver in kernel 5.17

graysky wrote:

Assuming you are force enabling the driver, it may work fine but it is likely not optimal.  See the comments in the code I linked above.

If you reread the entire thread, you will realize that I warned you of the same thing months ago, plus I experienced it on my own machine with stuttering in games. Now, I am telling you that amd-pstate + schedutil are working fine with no stuttering or slowdown while my CPU can idle at 550 Mhz. I don´t know if my power consumption has improved, but it just works fine this time.

Don't pay too much attention to the comments in the kernel code and try it yourself.


Excuse my poor English.

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#35 2022-08-15 20:08:59

graysky
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From: :wq
Registered: 2008-12-01
Posts: 10,419
Website

Re: using the amd-pstate driver in kernel 5.17

I'll wait but do what you will with your hardware tongue


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#36 2022-08-21 08:14:13

regulator
Member
Registered: 2020-01-15
Posts: 15

Re: using the amd-pstate driver in kernel 5.17

I saw that Pop_OS have now enabled amd pstate by default if its supported.

I tried to record some figures but it seems that power usage when idle, when watching a movie, and under max load are pretty similar between amd_pstate and the default ACPI driver. The main thing I notice is under amd.pstate the fan barely comes on when on battery power.

p.s. since kernel 5.19 my scaling issues with schedutil are fixed!

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#37 2022-09-09 22:31:48

agapito
Member
From: Spain
Registered: 2008-11-13
Posts: 551

Re: using the amd-pstate driver in kernel 5.17


Excuse my poor English.

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