88c56cfeae
CFS bandwidth limits and NOHZ full don't play well together. Tasks can easily run well past their quotas before a remote tick does accounting. This leads to long, multi-period stalls before such tasks can run again. Currently, when presented with these conflicting requirements the scheduler is favoring nohz_full and letting the tick be stopped. However, nohz tick stopping is already best-effort, there are a number of conditions that can prevent it, whereas cfs runtime bandwidth is expected to be enforced. Make the scheduler favor bandwidth over stopping the tick by setting TICK_DEP_BIT_SCHED when the only running task is a cfs task with runtime limit enabled. We use cfs_b->hierarchical_quota to determine if the task requires the tick. Add check in pick_next_task_fair() as well since that is where we have a handle on the task that is actually going to be running. Add check in sched_can_stop_tick() to cover some edge cases such as nr_running going from 2->1 and the 1 remains the running task. Reviewed-By: Ben Segall <bsegall@google.com> Signed-off-by: Phil Auld <pauld@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20230712133357.381137-3-pauld@redhat.com
106 lines
2.6 KiB
C
106 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* Only give sleepers 50% of their service deficit. This allows
|
|
* them to run sooner, but does not allow tons of sleepers to
|
|
* rip the spread apart.
|
|
*/
|
|
SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
|
|
|
|
/*
|
|
* Place new tasks ahead so that they do not starve already running
|
|
* tasks
|
|
*/
|
|
SCHED_FEAT(START_DEBIT, true)
|
|
|
|
/*
|
|
* Prefer to schedule the task we woke last (assuming it failed
|
|
* wakeup-preemption), since its likely going to consume data we
|
|
* touched, increases cache locality.
|
|
*/
|
|
SCHED_FEAT(NEXT_BUDDY, false)
|
|
|
|
/*
|
|
* Prefer to schedule the task that ran last (when we did
|
|
* wake-preempt) as that likely will touch the same data, increases
|
|
* cache locality.
|
|
*/
|
|
SCHED_FEAT(LAST_BUDDY, true)
|
|
|
|
/*
|
|
* Consider buddies to be cache hot, decreases the likeliness of a
|
|
* cache buddy being migrated away, increases cache locality.
|
|
*/
|
|
SCHED_FEAT(CACHE_HOT_BUDDY, true)
|
|
|
|
/*
|
|
* Allow wakeup-time preemption of the current task:
|
|
*/
|
|
SCHED_FEAT(WAKEUP_PREEMPTION, true)
|
|
|
|
SCHED_FEAT(HRTICK, false)
|
|
SCHED_FEAT(HRTICK_DL, false)
|
|
SCHED_FEAT(DOUBLE_TICK, false)
|
|
|
|
/*
|
|
* Decrement CPU capacity based on time not spent running tasks
|
|
*/
|
|
SCHED_FEAT(NONTASK_CAPACITY, true)
|
|
|
|
#ifdef CONFIG_PREEMPT_RT
|
|
SCHED_FEAT(TTWU_QUEUE, false)
|
|
#else
|
|
|
|
/*
|
|
* Queue remote wakeups on the target CPU and process them
|
|
* using the scheduler IPI. Reduces rq->lock contention/bounces.
|
|
*/
|
|
SCHED_FEAT(TTWU_QUEUE, true)
|
|
#endif
|
|
|
|
/*
|
|
* When doing wakeups, attempt to limit superfluous scans of the LLC domain.
|
|
*/
|
|
SCHED_FEAT(SIS_PROP, false)
|
|
SCHED_FEAT(SIS_UTIL, true)
|
|
|
|
/*
|
|
* Issue a WARN when we do multiple update_rq_clock() calls
|
|
* in a single rq->lock section. Default disabled because the
|
|
* annotations are not complete.
|
|
*/
|
|
SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
|
|
|
|
#ifdef HAVE_RT_PUSH_IPI
|
|
/*
|
|
* In order to avoid a thundering herd attack of CPUs that are
|
|
* lowering their priorities at the same time, and there being
|
|
* a single CPU that has an RT task that can migrate and is waiting
|
|
* to run, where the other CPUs will try to take that CPUs
|
|
* rq lock and possibly create a large contention, sending an
|
|
* IPI to that CPU and let that CPU push the RT task to where
|
|
* it should go may be a better scenario.
|
|
*/
|
|
SCHED_FEAT(RT_PUSH_IPI, true)
|
|
#endif
|
|
|
|
SCHED_FEAT(RT_RUNTIME_SHARE, false)
|
|
SCHED_FEAT(LB_MIN, false)
|
|
SCHED_FEAT(ATTACH_AGE_LOAD, true)
|
|
|
|
SCHED_FEAT(WA_IDLE, true)
|
|
SCHED_FEAT(WA_WEIGHT, true)
|
|
SCHED_FEAT(WA_BIAS, true)
|
|
|
|
/*
|
|
* UtilEstimation. Use estimated CPU utilization.
|
|
*/
|
|
SCHED_FEAT(UTIL_EST, true)
|
|
SCHED_FEAT(UTIL_EST_FASTUP, true)
|
|
|
|
SCHED_FEAT(LATENCY_WARN, false)
|
|
|
|
SCHED_FEAT(ALT_PERIOD, true)
|
|
SCHED_FEAT(BASE_SLICE, true)
|
|
|
|
SCHED_FEAT(HZ_BW, true)
|