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Thread: Linux's "Ondemand" Governor Is No Longer Fit

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  1. #1
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    Default Linux's "Ondemand" Governor Is No Longer Fit

    Phoronix: Linux's "Ondemand" Governor Is No Longer Fit

    By default the Linux kernel uses the "ondemand" CPU frequency governor for achieving maximum clock frequency when system load is high and a lower clock frequency when the system is idle. However, it turns out that for at least modern Intel CPUs, this is likely no longer the case. This default kernel choice may lead to poor battery life and performance for modern Linux systems...

    http://www.phoronix.com/vr.php?view=MTM3NDQ

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    I definitely have much longer battery life using onDemand than Performance on my AMD laptop, is this some weird Intel issue?

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    Quote Originally Posted by peppercats View Post
    I definitely have much longer battery life using onDemand than Performance on my AMD laptop, is this some weird Intel issue?
    No, OnDemand is still fine for AMD because its AMD. But this is about creating a driver that ACTUALLY does a good job (not a half--assed) job of managing the CPU in terms of power management / performance. Once AMD writes a new scaling driver, like Intel did for intel_pstate, you should switch to that.

    TL;DR: OnDemand is a half assed solution, new pstate drivers are the right solution. Intel only so far. AMD has to write their own.

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    Quote Originally Posted by Ericg View Post
    No, OnDemand is still fine for AMD because its AMD. But this is about creating a driver that ACTUALLY does a good job (not a half--assed) job of managing the CPU in terms of power management / performance. Once AMD writes a new scaling driver, like Intel did for intel_pstate, you should switch to that.

    TL;DR: OnDemand is a half assed solution, new pstate drivers are the right solution. Intel only so far. AMD has to write their own.
    Do you think that they will actually submit such code with them shutting down their OSRC and laying off their developers responsible for their cpufrq/PowerNow developers?

    http://www.phoronix.com/scan.php?pag...tem&px=MTIyMDQ

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    Quote Originally Posted by deanjo View Post
    Do you think that they will actually submit such code with them shutting down their OSRC and laying off their developers responsible for their cpufrq/PowerNow developers?

    http://www.phoronix.com/scan.php?pag...tem&px=MTIyMDQ
    I don't THINK AMD is gonna be in business within the next 5 years. And while I realize that does not exactly answer your question, in a way it does.

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    Quote Originally Posted by Ericg View Post
    I don't THINK AMD is gonna be in business within the next 5 years. And while I realize that does not exactly answer your question, in a way it does.
    Not possible. Even though AMD hardware is really unspectacular they beat Intel hands down in the performance-cost ratio. Intel can play the price game, but if they drop their prices to the level of AMD's there will most certainly be some silly lawsuit being filed on the grounds of the most heavily abused word in the industry: anti-competition. (or dumping, whatever).

    Not to mention AMD has some presence in the dedicated GPU market. Although the alleged performance of Haswell's onboard graphics core are destroying that presence...

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    Quote Originally Posted by peppercats View Post
    I definitely have much longer battery life using onDemand than Performance on my AMD laptop, is this some weird Intel issue?
    Contrary to some other responses in this thread, yes, that would be some weird intel fuckup. Performance governor basically does this; it sets everything to full speed all of the time. Even having to wake up once in a while will use less power than staying on maximum all of the time. That is, unless you do something REALLY stupid in your CPU design to make it operate like a fluorescent light and suck down more power during startup phase.

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    Quote Originally Posted by droidhacker View Post
    Contrary to some other responses in this thread, yes, that would be some weird intel fuckup. Performance governor basically does this; it sets everything to full speed all of the time. Even having to wake up once in a while will use less power than staying on maximum all of the time. That is, unless you do something REALLY stupid in your CPU design to make it operate like a fluorescent light and suck down more power during startup phase.
    Performance doesn't prevent it from going to idle, it can still idle its just at max freqs when not idling.

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    It's especially complicated these days since the CPU and GPU both share the same thermal headroom. Sometimes maxing out the CPU limits the GPU or vice-versa. I'm not really sure what the best solution is, but I'm glad people are looking into it. There are probably some decent gains to be had.

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    Quote Originally Posted by Kayden View Post
    It's especially complicated these days since the CPU and GPU both share the same thermal headroom. Sometimes maxing out the CPU limits the GPU or vice-versa. I'm not really sure what the best solution is, but I'm glad people are looking into it. There are probably some decent gains to be had.

    That came up during the rc6 development. rc6 bumped the GPU performance because the CPU could go lower thus using less heat and the GPU could then go higher using more heat because the CPU was using less.

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