AMD P-State vs. ACPI CPUFreq Testing With Ryzen Laptops On Linux 5.17

[birdie]

I think it would have been interesting to also include desktop CPU in the comparison because, on my 3900x, I see it hovering waaaaaay lower than it was either with acpi-cpufreq. And, I know some people will say that's useless to do "powersave" on desktop, but, from my point of view, there is no point to keep all cores at 1.2Ghz, when in fact the can be at 560Mhz (which is the kind of difference I'm talking about), because a) electricity cost quite a lot where I live, b) more heat -> fan have to turn faster -> more consumption, and even worse, more noise. (and in fact, I'm very jealous that, on windows, most of the time, a lot of cores are just "off", not slow, but off). But to be honest, I don't use too much schedutils, which for me is good at nothing, so I switch between powersave, conservative, and performance

acpi-cpufreq does not properly report the effective idle CPU frequency, thus your conclusions are not correct. With both acpi-cpufreq and amd-pstate idle cores are nearly completely idle, i.e. they don't consume any energy. I have verified this for my 5800X.

[blackshard]

all this effort to create diver that is same or worse than existing one...

That's because you ignore the purpose of amd-pstate-schedutil: try to give the best balance between performance and consumption. Some of the benchmarks clearly shows that (frames per watt ratios, for example), but the majority of these benchmarks miss the point.

[Linuxxx]

That's because you ignore the purpose of amd-pstate-schedutil: try to give the best balance between performance and consumption. Some of the benchmarks clearly shows that (frames per watt ratios, for example), but the majority of these benchmarks miss the point.

Then how come amd-pstate performance actually consumes less power on average than schedutil?

[Myownfriend]

I frequently use the powersave profile on my desktop because it's fine for every day tasks but the one thing I never understood was by the lowest frequency that Linux reports for my 5950X is 2200Mhz but Windows will go down to 1700Mhz. Overall, AMD's P-state driver is pretty disappointing but does it at least allow for lower minimum clock frequencies?

[Linuxxx]

I frequently use the powersave profile on my desktop because it's fine for every day tasks but the one thing I never understood was by the lowest frequency that Linux reports for my 5950X is 2200Mhz but Windows will go down to 1700Mhz. Overall, AMD's P-state driver is pretty disappointing but does it at least allow for lower minimum clock frequencies?

ACPI-cpufreq only reports three frequencies, but your AMD CPU will still enter C-states (sleep-states), which are the real power-savers, not lower frequencies.

And since you own a multi-CCX Ryzen 5950X:
How is the energy consumption with the performance governor during idle times?

Previously someone had reported rising temperatures with such a setup, which maybe could have something to do with increased Infinity Fabric activity.

Ever observed anything similar?

[birdie]

I frequently use the powersave profile on my desktop because it's fine for every day tasks but the one thing I never understood was by the lowest frequency that Linux reports for my 5950X is 2200Mhz but Windows will go down to 1700Mhz.

https://www.phoronix.com/forums/forum/phoronix/latest-phoronix-articles/1318666-amd-p-state-vs-acpi-cpufreq-testing-with-ryzen-laptops-on-linux-5-17?p=1318742#post1318742

Overall, AMD's P-state driver is pretty disappointing but does it at least allow for lower minimum clock frequencies?

If you like numbers than it does aside from https://bugzilla.kernel.org/show_bug.cgi?id=215729

[Linuxxx]

https://www.phoronix.com/forums/forum/phoronix/latest-phoronix-articles/1318666-amd-p-state-vs-acpi-cpufreq-testing-with-ryzen-laptops-on-linux-5-17?p=1318742#post1318742

If you like numbers than it does aside from https://bugzilla.kernel.org/show_bug.cgi?id=215729

So, with amd-pstate in idle:

Powersave and performance (!) governors ~ 20W.
Conservative ~ 21W.
Ondemand ~ 23.5W.

Thanks for doing these tests, Artem, but could you also add schedutil to the above mix, just to get the complete picture?

Thanks again!

[Mez']

Can't say it makes a compelling case to finally reboot any of my Zen2+ computers for the first time in 2022 with a 5.17 kernel (to enable the p-state driver)

[kiffmet]

phoronix Could you maybe test amd-pstate in conjunction with Alfred Chen's ProjectC/PDS scheduler and compare the results to the ones you got here in this article? CFS' thread distribution may be suboptimal on Ryzen when it comes to allowing for higher boost clocks. PDS is said to improve performance especially in gaming, which is where you've seen the greatest deficits with CFS + amd-pstate.

[Myownfriend]

https://www.phoronix.com/forums/foru...42#post1318742

If you like numbers than it does aside from https://bugzilla.kernel.org/show_bug.cgi?id=215729

That explains a lot. Thank you!

And since you own a multi-CCX Ryzen 5950X:
How is the energy consumption with the performance governor during idle times?

Previously someone had reported rising temperatures with such a setup, which maybe could have something to do with increased Infinity Fabric activity.

Ever observed anything similar?

I never really use the performance governor so I wouldn't know. I only really use schedutil and powersave.