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I have kernel 2.6.38 and Core2 Quad cpu - is there a way to manually manipulate cpu throttling (T-states)? All tutorials I've seen seem to suggest manipulating files under /proc/acpi/processor, ...
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    Throttling of Core2 Quad


    I have kernel 2.6.38 and Core2 Quad cpu - is there a way to manually manipulate cpu throttling (T-states)? All tutorials I've seen seem to suggest manipulating files under /proc/acpi/processor, but I don't even have such directory.

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    Linux Guru reed9's Avatar
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    I use cpufrequtils to manage cpu frequency.

    A lot of good information on the Arch Wiki, much of which is distro agnostic. Some details will vary system to system. For example, the Ubuntu package is called cpufrequtils. You will also need laptop-mode-tools, I believe, and then the config file in Ubuntu is /etc/laptop-mode/conf.d/cpufreq.conf.

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    Quote Originally Posted by reed9 View Post
    I use cpufrequtils to manage cpu frequency.
    Hmm, can I really use cpufrequtils to manage throttling? I mean, throttling doesn't mean changing cpu clock frequency (which I'm able to do, btw).

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    Linux Guru reed9's Avatar
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    I was thinking you meant dynamic frequency scaling which is indeed referred to as CPU throttling.

    I think with modern systems adjusting the T state isn't necessarily effective. You can do so with laptop-mode-tools still, under the setting CONTROL_CPU_THROTTLING, but not all CPUs support it.

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    I always doubted the fact that T states are indeed effective. Turning off the processor will reduce power consumption unlike reducing core frequency, of course for actual reduction in power consumption, you have to do less CPU intensive tasks along with throttling.

    I think more effective will be tweaking the ondemand governor to be less responsive.

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    Quote Originally Posted by dE_logics View Post
    I always doubted the fact that T states are indeed effective. Turning off the processor will reduce power consumption unlike reducing core frequency, of course for actual reduction in power consumption, you have to do less CPU intensive tasks along with throttling.

    I think more effective will be tweaking the ondemand governor to be less responsive.
    Yes, I can adjust the clock frequency of my CPU from 2GHz to 3GHz and it stays at 2Ghz about 99.9 % of the time when idle. But since my computer stands idle for several hours per day, I was thinking that aggressive throttling may effectively lower the cpu core temperature when idle.

    But unfortunately it seems that I can't use T-states with my Core2.

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    What's the output of -

    cat /proc/acpi/processor/cpu0/throttling

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    Quote Originally Posted by dE_logics View Post
    What's the output of -

    cat /proc/acpi/processor/cpu0/throttling

    I don't even have /proc/acpi/processor tree.

    The closest thing I have is /sys/devices/system/cpu/cpu0/thermal_throttle directory, but there is only core_throttle_count file.

    Is this something configurable (kernel/bios)?

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    Quote Originally Posted by bobca View Post
    I don't even have /proc/acpi/processor tree.

    The closest thing I have is /sys/devices/system/cpu/cpu0/thermal_throttle directory, but there is only core_throttle_count file.

    Is this something configurable (kernel/bios)?
    ACPI processor support.

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    Quote Originally Posted by dE_logics View Post
    ACPI processor support.
    Hmmh...

    Code:
    $ grep ACPI_PROCESSOR /boot/config-2.6.38-bpo.2-amd64
    CONFIG_ACPI_PROCESSOR=m
    and

    Code:
    $ lsmod |grep processor
    processor              27431  1 acpi_cpufreq
    thermal_sys            17939  1 processor
    But still nothing throttle specific under /proc

    I noticed that CONFIG_INTEL_IDLE is disabled (this is a Debian machine). Is that relevant?

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