Whether or not turbo P-states are supported at all. Add a Comment Sign in Have a technical question? Operation mode of the driver: This is roughly correct. I hope to be extending this soon. Without HWP, this P-state selection algorithm is always the same regardless of the processor model and platform configuration. This processor state is optional.

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By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. Some functionality of the core is limited by that.

They are not generic scaling governors, but their names are the same as the names of some of those governors. However, its configuration can be adjusted via sysfs to a great extent. I’m neglecting the effect of thermal inertia.

In truth, a P-state is both a frequency and voltage operating point. There are a host of other factors influencing runtime, such as cache size and speed, interrupts, etc.

Moreover, some processors support the Configurable TDP Thermal Design Power feature and, when that feature is enabled, the turbo threshold effectively becomes a configurable value that can be set by inttel platform firmware.

Namely, the Sandy Bridge generation of processors will psfate use any P-states above the last one set by software for the given core, even if it is within the turbo range, whereas all of the later processor generations will take it as a license to use any P-states from the turbo range, even above the one set by software.

With recent kernels, it is possible to disable it, in some cases, after boot.


If unset equalt to 0, which is the defaultturbo P-states can be set by the driver. It is similar to the algorithm implemented by the generic schedutil scaling governor except that the utilization metric used by it is based on numbers coming from feedback registers of the CPU. In other words, on those processors setting any P-state from the turbo range will enable the processor to put the given core into all turbo P-states up to and including the maximum supported one as it sees fit.

The meaning of these attributes in the passive mode is the same as for other scaling drivers.

So reducing the frequency reduces the peak thermal output even if the total energy usage is not reduced. The global and per-policy limits can be set independently. Thanks for that Doug. This processor state is optional.

Linux Intel P-State vs. CPUFreq Scaling Driver/Governor Benchmarks – Phoronix

The coordination between those limits is based on the following rules, regardless of the current operation mode of the driver: This was the case years ago with those ancient generations old processors. That only is supported in some configurations, though for example, if the HWP feature is enabled in the processorthe operation mode of the driver cannot be changedand if it is not supported in the current configuration, writes to this attribute with fail with an appropriate error.

This shouldn’t have any effect on the power usage of the processor. Although it often is possible to obtain all of it from the processor itself using model-specific registersthere are cases in which hardware manuals need to be consulted to get to it too.

This is where voltage scaling comes into play.


cpu – Change the cpufreq driver from intel pstate to acpi – Unix & Linux Stack Exchange

In turn, the P-states below the turbo threshold generally are sustainable. Like in the performance case, the hardware configuration is not touched if the new P-state turns out to be the same as pstahe current pstatee. In addition to the two good links Ravan gave, see also here and here. What those hints are depends on which P-state selection algorithm has been applied to the given policy or to the CPU it corresponds to.

What exactly is a P-state? (Pt. 1)

Are there any availiable data about how much energy the processor consumes in each p-state? Psgate, the limits are taken into account by scaling governors in the passive mode and by the driver every time before setting a new P-state for a CPU.

The reasons why you want to reduce the peak thermal load is pretty obvious.

C3 often known as Sleep is a state where the processor does not need to keep its cache coherentbut maintains other state. C1 often known as Halt is a state where the processor is not executing instructions, but can return to an executing state essentially instantaneously.

Home Questions Tags Users Unanswered. Now wait a moment.

Number of P-states supported by the processor between 0 and inclusive including both turbo and non-turbo P-states see Turbo P-states Support.