Lines Matching +full:space +full:- +full:constraint
1 .. SPDX-License-Identifier: GPL-2.0
11 feature that allows user space to help in managing the performance requirement
40 abstraction from user space point of view.
57 foreground, top-app, etc. Util clamp can be used to constrain how much
59 can run at. This constraint helps reserve resources for important tasks, like
60 the ones belonging to the currently active app (top-app group). Beside this
62 heterogeneous systems (e.g. Arm big.LITTLE); the constraint will help bias the
65 1. The big cores are free to run top-app tasks immediately. top-app
78 By making these uclamp performance requests, or rather hints, user space can
97 User space can form a feedback loop with the thermal subsystem too to ensure
106 Note that by design RT tasks don't have per-task PELT signal and must always
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
149 (struct uclamp_bucket) which allows us to reduce the search space from every
150 task on the rq to only a subset of tasks on the top-most bucket.
157 uclamp value of the rq. See :ref:`section 2.1 <uclamp-buckets>` for details on
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
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
295 particular for UCLAMP_MAX hint when user space would like to save power.
298 -----------------------------
311 :ref:`Section 3 <uclamp-interfaces>` discusses the interfaces and will expand
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>`.
391 * cpu.uclamp.max is a limit as described in :ref:`section 3-2 of cgroup v2
392 documentation <cgroupv2-limits-distributor>`.
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 --------------------------
451 they won't be satisfied until it is more than p->uclamp[UCLAMP_MIN].
456 --------------------------
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 -------------------------------------
525 Util clamp promotes the concept of user space assisted power and performance
527 decision. However, with util clamp user space can hint to the scheduler to make
543 4.1. Boost important and DVFS-latency-sensitive tasks
544 -----------------------------------------------------
564 -------------------------
571 -------------------
581 4.4. Per-app performance restriction
582 ------------------------------------
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
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