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Benchmarking The Intel P-State, CPUfreq Changes

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  • phoronix
    started a topic Benchmarking The Intel P-State, CPUfreq Changes

    Benchmarking The Intel P-State, CPUfreq Changes

    Phoronix: Benchmarking The Intel P-State, CPUfreq Changes

    On Friday there was the controversial news about the Linux "ondemand" cpufreq governor no longer being fit for best performance and power-savings on modern processors. Fortunately, for better handling the CPU frequency stage changes on modern Intel CPUs, Intel recently introduced the new P-State kernel driver...

    http://www.phoronix.com/vr.php?view=MTM3NTI

  • torsionbar28
    replied
    I leave mine set to Performance all the time. OnDemand has a noticeable impact on system responsiveness. As measured by a Kill-A-Watt meter at the power outlet, there is zero difference in power savings between OnDemand and Performance, while the machine is idle. When the machine is not idle, I don't care about power consumption, I want max performance and max responsiveness.

    This is for a desktop machine BTW. Laptops are different, and even fractions of a watt add up to less heat and more battery time in a laptop, so maybe these other governors have some value in the laptop world.

    Leave a comment:


  • gaubi
    replied
    Powersavings ?

    Hi,

    The pstate is around now for several weeks and I wonder if there are people, who have actually measured some energy savings.

    So, before I try my newest kernel compilation, are there any powertop measurements or similar which could show
    improvements in battery life. This is what concerns me most, I am not interested in playing high-cpu games but to hear
    experiences in normal programming/email/surfing usage.

    Thanks to all the others

    Leave a comment:


  • GreatEmerald
    replied
    Originally posted by droidhacker View Post
    Wow!!! LMFAO! Somebody doesn't know the first thing about frequency governors or how to test them. Unless there is something particularly broken about them, when maximum CPU is demanded, they will ALL ramp the CPU up to full power. PERIOD. END OF STORY. That means that there WILL BE no difference in peak performance, which means that testing the peak performance of them is entirely absurd!

    What you need to test is POWER CONSUMPTION and SYSTEM RESPONSIVENESS at low to moderate loads.
    Not the powersave ones, and conservative can affect the non-peak performance.

    Leave a comment:


  • droidhacker
    replied
    Wow!!! LMFAO! Somebody doesn't know the first thing about frequency governors or how to test them. Unless there is something particularly broken about them, when maximum CPU is demanded, they will ALL ramp the CPU up to full power. PERIOD. END OF STORY. That means that there WILL BE no difference in peak performance, which means that testing the peak performance of them is entirely absurd!

    What you need to test is POWER CONSUMPTION and SYSTEM RESPONSIVENESS at low to moderate loads.

    Leave a comment:


  • fenrus
    replied
    Originally posted by fenrus View Post
    The native P state driver does NOT use cpufreq governors.... no point selecting or setting them (in fact, nothing good can come out that so please just don't do that)
    also one general note: for benchmarks that run fully flat out, don't expect many changes; that's the easiest case where pretty much every governor will pick the highest performance point and stay there.
    the most interesting benchmarks for this sort of thing are cases where the cpu is not 100% busy.

    Leave a comment:


  • fenrus
    replied
    don't select governors.,...

    Originally posted by AnonymousCoward View Post
    95% does seem too high, honestly. Perhaps they designed it with the expectation that most CPU heavy loads would be hitting 100%.
    The native P state driver does NOT use cpufreq governors.... no point selecting or setting them (in fact, nothing good can come out that so please just don't do that)

    Leave a comment:


  • AnonymousCoward
    replied
    Originally posted by vadimg View Post
    Though I think the behavior of the ondemand governor can also be improved by tuning its parameters, e.g. the following seems to help on my system (though as I said I'm usually just switching to performance governor, so I didn't test it a lot):

    Code:
    echo 60 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
    This parameter is cpu load (%) that triggers increase of cpu freq, default value is 95%, but according to "cpupower monitor" cpu load per core is simply not reaching this threshold with most opengl apps and r600g for me, due to load balancing between cores etc.
    95% does seem too high, honestly. Perhaps they designed it with the expectation that most CPU heavy loads would be hitting 100%.

    Leave a comment:


  • Ericg
    replied
    Originally posted by GreatEmerald View Post
    Well, when using Arch or Gentoo, such unit files shouldn't be much of a problem. You're configuring everything manually, anyway.
    True, but I also like being able to go back to the wikis and run off them. So if I start deviating from the wiki's too much then I might forget what I ever did originally haha

    Leave a comment:


  • GreatEmerald
    replied
    Originally posted by Ericg View Post
    That works too, its just a personal preference for me to use the designated tool rather than hack together a unit file / shell script. But you are right, that would work
    Well, when using Arch or Gentoo, such unit files shouldn't be much of a problem. You're configuring everything manually, anyway.

    Leave a comment:

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