Lines Matching +full:cost +full:- +full:effective
1 .. SPDX-License-Identifier: GPL-2.0
57 foreground, top-app, etc. Util clamp can be used to constrain how much
60 the ones belonging to the currently active app (top-app group). Beside this
65 1. The big cores are free to run top-app tasks immediately. top-app
106 Note that by design RT tasks don't have per-task PELT signal and must always
110 when an RT task wakes up. This cost is unchanged by using uclamp. Uclamp only
114 See :ref:`section 3.4 <uclamp-default-values>` for default values and
115 :ref:`3.4.1 <sched-util-clamp-min-rt-default>` on how to change RT tasks
132 frequency selection as well as task placement to be most effective. Both of
150 task on the rq to only a subset of tasks on the top-most bucket.
153 and on dequeue it is decremented. This makes keeping track of the effective
156 As tasks are enqueued and dequeued, we keep track of the current effective
157 uclamp value of the rq. See :ref:`section 2.1 <uclamp-buckets>` for details on
160 Later at any path that wants to identify the effective uclamp value of the rq,
161 it will simply need to read this effective uclamp value of the rq at that exact
167 When a task wakes up, the scheduler will look at the current effective uclamp
173 at the current effective uclamp value of the rq which is influenced by the set
182 .. _uclamp-buckets:
185 ------------
195 +-----------+-----------+-----------+---- ----+-----------+
197 +-----------+-----------+-----------+---- ----+-----------+
199 +- p0 +- p3 +- p4
201 +- p1 +- p5
203 +- p2
210 To reduce the search space when trying to decide the effective uclamp value of
234 p->uclamp[UCLAMP_MIN] = 300
235 p->uclamp[UCLAMP_MAX] = 1024
241 The rq then keeps track of its current effective uclamp value for each
249 rq->uclamp[UCLAMP_MIN] = max(rq->uclamp[UCLAMP_MIN], p->uclamp[UCLAMP_MIN])
257 rq->uclamp[UCLAMP_MIN] = search_top_bucket_for_highest_value()
261 See :ref:`section 3.4 <uclamp-default-values>` for details on default values.
265 --------------------
279 p0->uclamp[UCLAMP_MIN] = 300
280 p0->uclamp[UCLAMP_MAX] = 900
282 p1->uclamp[UCLAMP_MIN] = 500
283 p1->uclamp[UCLAMP_MAX] = 500
290 rq->uclamp[UCLAMP_MIN] = max(300, 500) = 500
291 rq->uclamp[UCLAMP_MAX] = max(900, 500) = 900
293 As we shall see in :ref:`section 5.1 <uclamp-capping-fail>`, this max
298 -----------------------------
301 the actual applied (effective) value can be influenced by more than just the
304 The effective util clamp value of any task is restricted as follows:
311 :ref:`Section 3 <uclamp-interfaces>` discusses the interfaces and will expand
314 For now suffice to say that if a task makes a request, its actual effective
328 ----------
335 .. _uclamp-interfaces:
341 -----------------------
354 attr->sched_util_min = 40% * 1024;
355 attr->sched_util_max = 80% * 1024;
362 The special value -1 is used to reset the uclamp settings to the system
365 Note that resetting the uclamp value to system default using -1 is not the same
372 ---------------------
382 * cpu.uclamp.min is a protection as described in :ref:`section 3-3 of cgroup
383 v2 documentation <cgroupv2-protections-distributor>`.
388 In a cgroup hierarchy, effective cpu.uclamp.min is the max of (child,
391 * cpu.uclamp.max is a limit as described in :ref:`section 3-2 of cgroup v2
392 documentation <cgroupv2-limits-distributor>`.
397 In a cgroup hierarchy, effective cpu.uclamp.max is the min of (child,
404 p0->uclamp[UCLAMP_MIN] = // system default;
405 p0->uclamp[UCLAMP_MAX] = // system default;
407 p1->uclamp[UCLAMP_MIN] = 40% * 1024;
408 p1->uclamp[UCLAMP_MAX] = 50% * 1024;
410 cgroup0->cpu.uclamp.min = 20% * 1024;
411 cgroup0->cpu.uclamp.max = 60% * 1024;
413 cgroup1->cpu.uclamp.min = 60% * 1024;
414 cgroup1->cpu.uclamp.max = 100% * 1024;
420 p0->uclamp[UCLAMP_MIN] = cgroup0->cpu.uclamp.min = 20% * 1024;
421 p0->uclamp[UCLAMP_MAX] = cgroup0->cpu.uclamp.max = 60% * 1024;
423 p1->uclamp[UCLAMP_MIN] = 40% * 1024; // intact
424 p1->uclamp[UCLAMP_MAX] = 50% * 1024; // intact
430 p0->uclamp[UCLAMP_MIN] = cgroup1->cpu.uclamp.min = 60% * 1024;
431 p0->uclamp[UCLAMP_MAX] = cgroup1->cpu.uclamp.max = 100% * 1024;
433 p1->uclamp[UCLAMP_MIN] = cgroup1->cpu.uclamp.min = 60% * 1024;
434 p1->uclamp[UCLAMP_MAX] = 50% * 1024; // intact
440 ---------------------
443 --------------------------
446 which means that permitted effective UCLAMP_MIN range for tasks is [0:1024].
451 they won't be satisfied until it is more than p->uclamp[UCLAMP_MIN].
456 --------------------------
459 which means that permitted effective UCLAMP_MAX range for tasks is [0:1024].
461 By changing it to 512 for example the effective allowed range reduces to
472 won't be satisfied until it is more than p->uclamp[UCLAMP_MAX].
476 .. _uclamp-default-values:
479 -------------------
485 p_fair->uclamp[UCLAMP_MIN] = 0
486 p_fair->uclamp[UCLAMP_MAX] = 1024
496 p_rt->uclamp[UCLAMP_MIN] = 1024
497 p_rt->uclamp[UCLAMP_MAX] = 1024
505 .. _sched-util-clamp-min-rt-default:
508 -------------------------------------
543 4.1. Boost important and DVFS-latency-sensitive tasks
544 -----------------------------------------------------
564 -------------------------
571 -------------------
581 4.4. Per-app performance restriction
582 ------------------------------------
586 limit it from draining system power at the cost of reduced performance for
597 .. _uclamp-capping-fail:
600 ---------------------------------------------------------------------
606 p0->uclamp[UCLAMP_MAX] = 512
612 p1->uclamp[UCLAMP_MAX] = 1024
619 rq->uclamp[UCLAMP_MAX] = max(512, 1024) = 1024
630 ------------------------------------------------
645 p0->util_avg = 300
646 p0->uclamp[UCLAMP_MAX] = 0
655 rq->uclamp[UCLAMP_MAX] = 0
665 long as there's idle time, p->util_avg updates will be off by a some margin,
670 p0->util_avg = 300 + small_error
683 p0->util_avg = 1024
689 p1->util_avg = 200
690 p1->uclamp[UCLAMP_MAX] = 1024
692 then the effective UCLAMP_MAX for the CPU will be 1024 according to max
694 severely, then the rq->util_avg will be:
698 p0->util_avg = 1024
699 p1->util_avg = 200
701 rq->util_avg = 1024
702 rq->uclamp[UCLAMP_MAX] = 1024
708 p0->util_avg = 300
709 p1->util_avg = 200
711 rq->util_avg = 500
716 -----------------------------------
720 1. Hardware takes non-zero time to respond to any frequency change
722 2. Non fast-switch systems require a worker deadline thread to wake up