Lines Matching full:it
18 (``CPUFreq``). It is a scaling driver for the Sandy Bridge and later
20 may not be supported. [To understand ``intel_pstate`` it is necessary to know
31 frequencies are involved in the user space interface exposed by it, so
33 (fortunately, that mapping is unambiguous). At the same time, it would not be
35 available frequencies due to the possible size of it, so the driver does not do
44 it goes back online.
46 ``intel_pstate`` is not modular, so it cannot be unloaded, which means that the
47 only way to pass early-configuration-time parameters to it is via the kernel
49 great extent. In some configurations it even is possible to unregister it via
58 active mode, it uses its own internal performance scaling governor algorithm or
60 mode it responds to requests made by a generic ``CPUFreq`` governor implementing
69 hardware-managed P-states (HWP) support. If it works in this mode, the
85 (roughly, it corresponds to the ``schedutil`` and ``ondemand`` governors).
95 default, and the other one will be used by default if it is not set.
100 If the processor supports the HWP feature, it will be enabled during the
101 processor initialization and cannot be disabled after that. It is possible
102 to avoid enabling it by passing the ``intel_pstate=no_hwp`` argument to the
106 select P-states by itself, but still it can give hints to the processor's
108 selection algorithm has been applied to the given policy (or to the CPU it
139 Energy-Performance Bias (EPB) knob (otherwise) to whatever value it was
140 previously set to via ``sysfs`` (or whatever default value it was
152 recognized by it. [Note that ``intel_pstate`` will never refuse to work with
168 It selects the maximum P-state it is allowed to use, subject to limits set via
181 utilization metric used by it is based on numbers coming from feedback
182 registers of the CPU. It generally selects P-states proportional to the
186 given CPU when it is invoked by the CPU scheduler, but not more often than
199 hardware-managed P-states (HWP) support. It is always used if the
203 if it is not combined with ``intel_pstate=active``.] Like in the active mode
205 processors that are not recognized by it if HWP is prevented from being enabled
211 it is invoked by generic scaling governors when necessary to talk to the
213 ``schedutil`` governor can invoke it directly from scheduler context).
218 used). Then, it is responsible for the configuration of policy objects
249 performance scaling control for that core and put it into turbo P-states of its
253 the given core, even if it is within the turbo range, whereas all of the later
254 processor generations will take it as a license to use any P-states from the
258 supported one as it sees fit.
263 package may change over time or the thermal envelope it was designed for might
268 it to a lower one unless in a thermal stress or a power limit violation
269 situation (a higher P-state may still be used if it is set for another CPU in
298 work as expected in all cases (that is, if set to disable turbo P-states, it
306 pieces of information on it to be known, including:
321 or family. Although it often is possible to obtain all of it from the processor
323 manuals need to be consulted to get to it too.
327 list, unless it supports the HWP feature. [The interface to obtain all of the
339 and it assumes the HWP performance units to be the same for all CPUs in the
358 it also leads to excessive energy usage in some important scenarios, like video
372 amount of spare capacity on it, and if the utilization of a given task is too
373 high for it, the task will need to go somewhere else.
375 Since CAS takes CPU capacities into account, it does not require CPU
376 prioritization and it allows tasks to be distributed more symmetrically among
378 capacity to accommodate it, a task may just continue to run there regardless of
385 the system and it needs to be able to compute scale-invariant utilization of
386 CPUs, so ``intel_pstate`` provides it with the requisite information.
393 regardless of the frequency it is currently running at, are adjusted to take the
395 registered itself with the ``CPUFreq`` core and it has figured out that it is
403 `CAS <CAS_>`_ it registers an Energy Model for the processor. This allows the
408 The Energy Model registered by ``intel_pstate`` is artificial (that is, it is
409 based on abstract cost values and it does not include any real power numbers)
410 and it is relatively simple to avoid unnecessary computations in the scheduler.
411 There is a performance domain in it for every CPU in the system and the cost
468 This attribute is present only if the value exposed by it is the same
480 This attribute is present only if the value exposed by it is the same
497 but it affects the maximum possible value of per-policy P-state limits
503 the processor. If set (equal to 1), it causes the minimum P-state limit
509 is directly set to the highest non-turbo P-state or above it.
525 The driver is not functional (it is not registered as a scaling
529 operation mode or to unregister it. The string written to it must be
530 one of the possible values of it and, if successful, the write will
545 optimizations are done only in the turbo frequency range. Without it,
555 as the current scaling driver and it generally depends on the driver's
569 ``scaling_min_freq`` to go down to that value if they were above it before.
604 depends on the operation mode of the driver. Namely, it is either
621 2. Each individual CPU is affected by its own per-policy limits (that is, it
622 cannot be requested to run faster than its own per-policy maximum and it
652 processor's internal P-state selection logic by focusing it on performance or on
658 (or the CPU represented by it).
673 Energy-Performance Bias (EPB) knob. It is also possible to write a positive
682 issues it is better to set the same energy vs performance hint for all CPUs
699 interface, but the set of P-states it can use is limited by the ``_PSS``
705 `turbo range <turbo_>`_ is represented by one item in it (the topmost one). By
707 than the frequency of the highest non-turbo P-state listed by it, but the
709 returned for it matches the maximum supported turbo P-state (or is the
715 it come from that list as well. In particular, given the special representation
724 (possibly multiplied by a constant), then it will tend to choose P-states below
727 band it can use (1 MHz vs 1 GHz or more). In consequence, it will only go to
740 the list returned by it.
743 `passive mode <Passive Mode_>`_, except that the number of P-states it can set
751 parameters to ``intel_pstate`` in order to enforce specific behavior of it. All
756 processor is supported by it.
772 information from functioning as expected, so it should be used with
780 Do not enable the hardware-managed P-states (HWP) feature even if it is
813 it works in the `active mode <Active Mode_>`_.
827 scaling governor (for the policies it is attached to), or by the ``CPUFreq``