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549020c814
Now that the mainline EAS wake-up path has been extended to cope with
prefer-idle tasks, the need for a dedicated Android-specific wake-up
routine (find_best_target()) becomes less clear. Indeed, main reasons
for introducting find_best_target() in the first place were:
1. the energy_diff function was very slow, so we couldn't afford to
use it on all CPUs for each wake-up for latency reasons;
2. schedtune provides additional information about tasks (the
prefer-idle flag in particular) which needed to be taken into
account in the placement algorithm.
Now that the energy diff calculation is much faster (with the simplified
energy model) and that the EAS path is aware of prefer-idle tasks, there
is no clear reason to use find_best_target() any more.
So, let's disable it for now to minimize the amount of out-of-tree code
used in the scheduler. If using the mainline path doesn't cause
regressions, it is a good sign find_best_target() can be removed safely,
eventually. Otherwise, reverting back to the old behaviour is trivial
since this patch only changes the sched_feat default, but doesn't remove
the fbt() code path.
Bug: 120440300
Change-Id: Idb5d68a3c4af7d2212e0922ab6d9a089170b5e1c
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
123 lines
3.3 KiB
C
123 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Only give sleepers 50% of their service deficit. This allows
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* them to run sooner, but does not allow tons of sleepers to
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* rip the spread apart.
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*/
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SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
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/*
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* Place new tasks ahead so that they do not starve already running
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* tasks
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*/
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SCHED_FEAT(START_DEBIT, true)
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/*
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* Prefer to schedule the task we woke last (assuming it failed
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* wakeup-preemption), since its likely going to consume data we
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* touched, increases cache locality.
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*/
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SCHED_FEAT(NEXT_BUDDY, false)
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/*
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* Prefer to schedule the task that ran last (when we did
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* wake-preempt) as that likely will touch the same data, increases
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* cache locality.
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*/
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SCHED_FEAT(LAST_BUDDY, true)
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/*
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* Consider buddies to be cache hot, decreases the likelyness of a
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* cache buddy being migrated away, increases cache locality.
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*/
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SCHED_FEAT(CACHE_HOT_BUDDY, true)
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/*
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* Allow wakeup-time preemption of the current task:
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*/
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SCHED_FEAT(WAKEUP_PREEMPTION, true)
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SCHED_FEAT(HRTICK, false)
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SCHED_FEAT(DOUBLE_TICK, false)
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SCHED_FEAT(LB_BIAS, true)
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/*
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* Decrement CPU capacity based on time not spent running tasks
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*/
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SCHED_FEAT(NONTASK_CAPACITY, true)
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/*
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* Queue remote wakeups on the target CPU and process them
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* using the scheduler IPI. Reduces rq->lock contention/bounces.
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*/
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SCHED_FEAT(TTWU_QUEUE, true)
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/*
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* When doing wakeups, attempt to limit superfluous scans of the LLC domain.
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*/
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SCHED_FEAT(SIS_AVG_CPU, false)
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SCHED_FEAT(SIS_PROP, true)
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/*
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* Issue a WARN when we do multiple update_rq_clock() calls
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* in a single rq->lock section. Default disabled because the
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* annotations are not complete.
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*/
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SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
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#ifdef HAVE_RT_PUSH_IPI
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/*
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* In order to avoid a thundering herd attack of CPUs that are
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* lowering their priorities at the same time, and there being
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* a single CPU that has an RT task that can migrate and is waiting
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* to run, where the other CPUs will try to take that CPUs
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* rq lock and possibly create a large contention, sending an
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* IPI to that CPU and let that CPU push the RT task to where
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* it should go may be a better scenario.
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*/
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SCHED_FEAT(RT_PUSH_IPI, true)
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#endif
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SCHED_FEAT(RT_RUNTIME_SHARE, true)
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SCHED_FEAT(LB_MIN, false)
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SCHED_FEAT(ATTACH_AGE_LOAD, true)
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SCHED_FEAT(WA_IDLE, true)
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SCHED_FEAT(WA_WEIGHT, true)
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SCHED_FEAT(WA_BIAS, true)
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/*
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* UtilEstimation. Use estimated CPU utilization.
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*/
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SCHED_FEAT(UTIL_EST, true)
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/*
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* Fast pre-selection of CPU candidates for EAS.
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*/
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SCHED_FEAT(FIND_BEST_TARGET, false)
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/*
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* Energy aware scheduling algorithm choices:
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* EAS_PREFER_IDLE
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* Direct tasks in a schedtune.prefer_idle=1 group through
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* the EAS path for wakeup task placement. Otherwise, put
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* those tasks through the mainline slow path.
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*/
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SCHED_FEAT(EAS_PREFER_IDLE, true)
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/*
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* Request max frequency from schedutil whenever a RT task is running.
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*/
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SCHED_FEAT(SUGOV_RT_MAX_FREQ, false)
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/*
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* Apply schedtune boost hold to tasks of all sched classes.
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* If enabled, schedtune will hold the boost applied to a CPU
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* for 50ms regardless of task activation - if the task is
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* still running 50ms later, the boost hold expires and schedtune
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* boost will expire immediately the task stops.
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* If disabled, this behaviour will only apply to tasks of the
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* RT class.
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*/
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SCHED_FEAT(SCHEDTUNE_BOOST_HOLD_ALL, false)
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