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New AMD P-State Driver Headlines The Power Management Updates For Linux 5.17

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  • #21
    Originally posted by agd5f View Post

    If you are working a document in a word processor or doing some web browsing, there no need to ramp the the CPU to the max frequency constantly every time that task schedules. The user experience of working with that document will be the same whether or not the CPU is at the max frequency or not. As I said, the tricky part is deciding what the right algorithm is in the governor. These patches just provide the knobs. The governors still dictate the performance.
    Maybe my question was misplaced, let me rephrase it. In theory I have nothing against being able to select more frequencies, but I think it's an overly difficult task for the governor being able to select the right one depending on your workload. In real world scenarios it fails to ramp up sustained workloads which definitely need the maximum power, like encoding. In real world usage pstate equals crippling your cpu in most scenarios, effectively making a 600$ CPU worth like a 100$ one. I would like to say that I'm not against the concept but rather against the execution, but reality is that deciding the right frequency is an impossible task for the governor.
    ## VGA ##
    AMD: X1950XTX, HD3870, HD5870
    Intel: GMA45, HD3000 (Core i5 2500K)

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    • #22
      Originally posted by darkbasic View Post

      Maybe my question was misplaced, let me rephrase it. In theory I have nothing against being able to select more frequencies, but I think it's an overly difficult task for the governor being able to select the right one depending on your workload. In real world scenarios it fails to ramp up sustained workloads which definitely need the maximum power, like encoding. In real world usage pstate equals crippling your cpu in most scenarios, effectively making a 600$ CPU worth like a 100$ one. I would like to say that I'm not against the concept but rather against the execution, but reality is that deciding the right frequency is an impossible task for the governor.
      Why even offer multiple speeds? Everyone should just use CPUs with fixed clocks. Is this actually crippling in practice or are you just concerned that benchmarks are lower so it must mean that it is? The idea is that the system should have good responsiveness and usability, not the absolute maximum performance. If you want max performance, use a performance governor.

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      • #23
        Originally posted by agd5f View Post

        Why even offer multiple speeds? Everyone should just use CPUs with fixed clocks. Is this actually crippling in practice or are you just concerned that benchmarks are lower so it must mean that it is? The idea is that the system should have good responsiveness and usability, not the absolute maximum performance. If you want max performance, use a performance governor.
        My CPU is just a Zen1 so I have not been able to test P-State, but from my past experience with Intel CPUs yes, it was crippling in practice. What I mean with crippling is that it failed to ramp all the way up with some sustained workloads, while acpi-cpufreq didn't. That means I had to manually select the performance governor each time I wanted to run these workloads if I didn't want them to take longer. Hopefully these issues are solved now, but my experience with p-state has never been good.
        ## VGA ##
        AMD: X1950XTX, HD3870, HD5870
        Intel: GMA45, HD3000 (Core i5 2500K)

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