kernel/sched/features.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 /*
0003  * Only give sleepers 50% of their service deficit. This allows
0004  * them to run sooner, but does not allow tons of sleepers to
0005  * rip the spread apart.
0006  */
0007 SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
0008
0009 /*
0010  * Place new tasks ahead so that they do not starve already running
0011  * tasks
0012  */
0013 SCHED_FEAT(START_DEBIT, true)
0014
0015 /*
0016  * Prefer to schedule the task we woke last (assuming it failed
0017  * wakeup-preemption), since its likely going to consume data we
0018  * touched, increases cache locality.
0019  */
0020 SCHED_FEAT(NEXT_BUDDY, false)
0021
0022 /*
0023  * Prefer to schedule the task that ran last (when we did
0024  * wake-preempt) as that likely will touch the same data, increases
0025  * cache locality.
0026  */
0027 SCHED_FEAT(LAST_BUDDY, true)
0028
0029 /*
0030  * Consider buddies to be cache hot, decreases the likeliness of a
0031  * cache buddy being migrated away, increases cache locality.
0032  */
0033 SCHED_FEAT(CACHE_HOT_BUDDY, true)
0034
0035 /*
0036  * Allow wakeup-time preemption of the current task:
0037  */
0038 SCHED_FEAT(WAKEUP_PREEMPTION, true)
0039
0040 SCHED_FEAT(HRTICK, false)
0041 SCHED_FEAT(HRTICK_DL, false)
0042 SCHED_FEAT(DOUBLE_TICK, false)
0043
0044 /*
0045  * Decrement CPU capacity based on time not spent running tasks
0046  */
0047 SCHED_FEAT(NONTASK_CAPACITY, true)
0048
0049 #ifdef CONFIG_PREEMPT_RT
0050 SCHED_FEAT(TTWU_QUEUE, false)
0051 #else
0052
0053 /*
0054  * Queue remote wakeups on the target CPU and process them
0055  * using the scheduler IPI. Reduces rq->lock contention/bounces.
0056  */
0057 SCHED_FEAT(TTWU_QUEUE, true)
0058 #endif
0059
0060 /*
0061  * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
0062  */
0063 SCHED_FEAT(SIS_PROP, false)
0064 SCHED_FEAT(SIS_UTIL, true)
0065
0066 /*
0067  * Issue a WARN when we do multiple update_rq_clock() calls
0068  * in a single rq->lock section. Default disabled because the
0069  * annotations are not complete.
0070  */
0071 SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
0072
0073 #ifdef HAVE_RT_PUSH_IPI
0074 /*
0075  * In order to avoid a thundering herd attack of CPUs that are
0076  * lowering their priorities at the same time, and there being
0077  * a single CPU that has an RT task that can migrate and is waiting
0078  * to run, where the other CPUs will try to take that CPUs
0079  * rq lock and possibly create a large contention, sending an
0080  * IPI to that CPU and let that CPU push the RT task to where
0081  * it should go may be a better scenario.
0082  */
0083 SCHED_FEAT(RT_PUSH_IPI, true)
0084 #endif
0085
0086 SCHED_FEAT(RT_RUNTIME_SHARE, false)
0087 SCHED_FEAT(LB_MIN, false)
0088 SCHED_FEAT(ATTACH_AGE_LOAD, true)
0089
0090 SCHED_FEAT(WA_IDLE, true)
0091 SCHED_FEAT(WA_WEIGHT, true)
0092 SCHED_FEAT(WA_BIAS, true)
0093
0094 /*
0095  * UtilEstimation. Use estimated CPU utilization.
0096  */
0097 SCHED_FEAT(UTIL_EST, true)
0098 SCHED_FEAT(UTIL_EST_FASTUP, true)
0099
0100 SCHED_FEAT(LATENCY_WARN, false)
0101
0102 SCHED_FEAT(ALT_PERIOD, true)
0103 SCHED_FEAT(BASE_SLICE, true)