Lines Matching full:state
44 enter an idle state, that applies to the processor as a whole.
52 enter an idle state, that applies to the core that asked for it in the first
57 remaining core asks the processor to enter an idle state, that may trigger it
58 to put the whole larger unit into an idle state which also will affect the
69 time management perspective and if the processor is asked to enter an idle state
72 core also have asked the processor to enter an idle state. In that situation,
73 the core may be put into an idle state individually or a larger unit containing
74 it may be put into an idle state as a whole (if the other cores within the
106 idle states, or there is not enough time to spend in an idle state before the
119 idle time management subsystem called ``CPUIdle`` to select an idle state for
122 processor hardware to enter the idle state selected by the governor.
124 The role of the governor is to find an idle state most suitable for the
133 Each idle state present in that array is characterized by two parameters to be
136 spend in the given state, including the time needed to enter it (which may be
138 the shallower idle states instead. [The "depth" of an idle state roughly
139 corresponds to the power drawn by the processor in that state.] The exit
141 hardware to enter an idle state to start executing the first instruction after a
142 wakeup from that state. Note that in general the exit latency also must cover
143 the time needed to enter the given state in case the wakeup occurs when the
151 CPU depends on can spend in an idle state, including the time necessary to enter
227 be harmful. Namely, in that case the governor will select an idle state with
228 the target residency within the time until the expected wakeup, so that state is
230 state then, as that would contradict its own expectation of a wakeup in short
235 in the shallow idle state selected by the governor, which will be a waste of
238 governor will select a relatively deep idle state, so the tick should be stopped
268 Namely, when invoked to select an idle state for a CPU (i.e. an idle state that
270 idle duration and uses the predicted value for idle state selection.
286 selecting the idle state for the CPU) is updated after the CPU has been woken
310 idle state is comparable with the predicted idle duration, the total time spent
311 in that state probably will be very short and the amount of energy to save by
313 overhead related to entering that state and exiting it. Thus selecting a
314 shallower state is likely to be a better option then. The first approximation
324 them. For this purpose, it compares the target residency of each state with
326 limit. It selects the state with the target residency closest to the predicted
330 In the final step the governor may still need to refine the idle state selection
336 that time, the governor may need to select a shallower state with a suitable
347 <menu-gov_>`_: it always tries to find the deepest idle state suitable for the
352 and use that information to pick up the idle state that is most likely to
365 idle state on the basis of three metrics maintained for each idle state provided
369 state will "match" the observed (post-wakeup) idle duration if it "matches" the
371 the target residency of the idle state corresponding to them is less than or
372 equal to the sleep length and the target residency of the next idle state is
373 greater than the sleep length (that is, when the idle state corresponding to
375 former condition is satisfied and the target residency of the given idle state
377 the next idle state is greater than the observed idle duration at the same time
378 (that is, it is increased when the given idle state "matches" both the sleep
380 increased when the given idle state "matches" the sleep length only and the
383 The ``early_hits`` metric measures the likelihood that a given idle state will
386 when the idle state corresponding to it "matches" the observed (post-wakeup)
387 idle duration and the target residency of the next idle state is less than or
388 equal to the sleep length (i.e. the idle state "matching" the sleep length is
394 state are compared with each other and it is preselected if the ``hits`` one is
395 greater (which means that that idle state is likely to "match" the observed idle
397 preselects the shallower idle state with the maximum ``early_hits`` metric
401 <cpu-pm-qos_>`_ which is hit before reaching the deepest idle state with the
402 target residency within the sleep length, the deepest idle state with the exit
408 the target residency of the preselected idle state, that idle state becomes the
410 duration values below the target residency of the preselected idle state is
413 That idle state is then taken as the final candidate to ask for.
415 Still, at this point the governor may need to refine the idle state selection if
417 generally happens if the target residency of the idle state selected so far is
422 than that time, a shallower state with a suitable target residency may need to
434 the processor hardware to enter an idle state of certain properties. If there
438 of it <idle-loop_>`_, must reflect the properties of the idle state at the
439 deepest level (i.e. the idle state of the unit containing all of the other
443 a "module" and suppose that asking the hardware to enter a specific idle state
445 enter a specific idle state of its own (say "MX") if the other core is in idle
446 state "X" already. In other words, asking for idle state "X" at the "core"
447 level gives the hardware a license to go as deep as to idle state "MX" at the
449 asking for idle state "X" may just end up in that state by itself instead).
451 idle state "X" must reflect the minimum time to spend in idle state "MX" of
454 that state. Analogously, the exit latency parameter of that object must cover
455 the exit time of idle state "MX" of the module (and usually its entry time too),
463 state at the "core" level does not automatically affect the "module" level, for
465 handling of the hierarchy. Then, the definition of the idle state objects is
466 entirely up to the driver, but still the physical properties of the idle state
468 used by the governor for idle state selection (for instance, the actual exit
469 latency of that idle state must not exceed the exit latency parameter of the
470 idle state object selected by the governor).
472 In addition to the target residency and exit latency idle state parameters
474 parameters describing the idle state and a pointer to the function to run in
475 order to ask the hardware to enter that state. Also, for each
478 statistics of the given idle state. That information is exposed by the kernel
484 called :file:`state0`, :file:`state1` and so on, up to the number of idle state
486 corresponds to one idle state object and the larger the number in its name, the
487 deeper the (effective) idle state represented by it. Each of them contains
488 a number of files (attributes) representing the properties of the idle state
492 Total number of times this idle state had been asked for, but the
497 Total number of times this idle state had been asked for, but certainly
498 a deeper idle state would have been a better match for the observed idle
502 Description of the idle state.
505 Whether or not this idle state is disabled.
508 The default status of this state, "enabled" or "disabled".
511 Exit latency of the idle state in microseconds.
514 Name of the idle state.
517 Power drawn by hardware in this idle state in milliwatts (if specified,
521 Target residency of the idle state in microseconds.
524 Total time spent in this idle state by the given CPU (as measured by the
529 enter this idle state.
532 Total number of times a request to enter this idle state on the given
541 given idle state is disabled for this particular CPU, which means that the
544 However, disabling an idle state for one CPU does not prevent it from being
547 governor is implemented, disabling an idle state prevents that governor from
550 If the :file:`disable` attribute contains 0, the given idle state is enabled for
552 CPUs in the system at the same time. Writing 1 to it causes the idle state to
555 unless that state was disabled globally in the driver (in which case it cannot
558 The :file:`power` attribute is not defined very well, especially for idle state
561 state power numbers for complex hardware, so :file:`power` often contains 0 (not
566 really spent by the given CPU in the given idle state, because it is measured by
568 this idle state and entered a shallower one instead of it (or even it did not
569 enter any idle state at all). The kernel can only measure the time span between
570 asking the hardware to enter an idle state and the subsequent wakeup of the CPU
572 Moreover, if the idle state object in question represents a combination of idle
577 it is to use idle state residency counters in the hardware, if available.
579 Generally, an interrupt received when trying to enter an idle state causes the
580 idle state entry request to be rejected, in which case the ``CPUIdle`` driver
582 and :file:`rejected` files report the number of times the given idle state
700 and causes the hardware to attempt to enter the shallowest available idle state)
723 where ``<n>`` is an idle state index also used in the name of the given
724 state's directory in ``sysfs`` (see
727 idle states deeper than idle state ``<n>``. In that case, they will never ask