These two scheduler features have a high impact on performance for some database workloads. Move them to sysctl as they are likely to be modified and persisted across reboots.

Cc: stable@vger.kernel.org # 6.6.x Fixes: 86bfbb7ce4f6 ("sched/fair: Add lag based placement") Fixes: 63304558ba5d ("sched/eevdf: Curb wakeup-preemption") Signed-off-by: Cristian Prundeanu cpru@amazon.com --- include/linux/sched/sysctl.h | 8 ++++++++ kernel/sched/core.c | 13 +++++++++++++ kernel/sched/fair.c | 5 +++-- kernel/sched/features.h | 10 ---------- kernel/sysctl.c | 20 ++++++++++++++++++++ 5 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index 5a64582b086b..0258fba3896a 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -29,4 +29,12 @@ extern int sysctl_numa_balancing_mode; #define sysctl_numa_balancing_mode 0 #endif

+#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL) +extern unsigned int sysctl_sched_place_lag_enabled; +extern unsigned int sysctl_sched_run_to_parity_enabled; +#else +#define sysctl_sched_place_lag_enabled 0 +#define sysctl_sched_run_to_parity_enabled 0 +#endif + #endif /* _LINUX_SCHED_SYSCTL_H */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 43e453ab7e20..c6bd1bda8c7e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -134,6 +134,19 @@ const_debug unsigned int sysctl_sched_features = 0; #undef SCHED_FEAT

+#ifdef CONFIG_SYSCTL +/* + * Using the avg_vruntime, do the right thing and preserve lag across + * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled. + */ +__read_mostly unsigned int sysctl_sched_place_lag_enabled = 0; +/* + * Inhibit (wakeup) preemption until the current task has either matched the + * 0-lag point or until is has exhausted it's slice. + */ +__read_mostly unsigned int sysctl_sched_run_to_parity_enabled = 0; +#endif + /* * Print a warning if need_resched is set for the given duration (if * LATENCY_WARN is enabled). diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5a621210c9c1..c58b76233f59 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -925,7 +925,8 @@ static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq) * Once selected, run a task until it either becomes non-eligible or * until it gets a new slice. See the HACK in set_next_entity(). */ - if (sched_feat(RUN_TO_PARITY) && curr && curr->vlag == curr->deadline) + if (sysctl_sched_run_to_parity_enabled && + curr && curr->vlag == curr->deadline) return curr;

/* Pick the leftmost entity if it's eligible */ @@ -5280,7 +5281,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) * * EEVDF: placement strategy #1 / #2 */ - if (sched_feat(PLACE_LAG) && cfs_rq->nr_running && se->vlag) { + if (sysctl_sched_place_lag_enabled && cfs_rq->nr_running && se->vlag) { struct sched_entity *curr = cfs_rq->curr; unsigned long load;

diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 8a5ca80665b3..b39a9dde0b54 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -1,10 +1,5 @@ /* SPDX-License-Identifier: GPL-2.0 */

-/* - * Using the avg_vruntime, do the right thing and preserve lag across - * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled. - */ -SCHED_FEAT(PLACE_LAG, false) /* * Give new tasks half a slice to ease into the competition. */ @@ -13,11 +8,6 @@ SCHED_FEAT(PLACE_DEADLINE_INITIAL, true) * Preserve relative virtual deadline on 'migration'. */ SCHED_FEAT(PLACE_REL_DEADLINE, true) -/* - * Inhibit (wakeup) preemption until the current task has either matched the - * 0-lag point or until is has exhausted it's slice. - */ -SCHED_FEAT(RUN_TO_PARITY, false) /* * Allow wakeup of tasks with a shorter slice to cancel RUN_TO_PARITY for * current. diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 79e6cb1d5c48..f435b741654a 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -2029,6 +2029,26 @@ static struct ctl_table kern_table[] = { .extra2 = SYSCTL_INT_MAX, }, #endif +#ifdef CONFIG_SCHED_DEBUG + { + .procname = "sched_place_lag_enabled", + .data = &sysctl_sched_place_lag_enabled, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { + .procname = "sched_run_to_parity_enabled", + .data = &sysctl_sched_run_to_parity_enabled, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, +#endif };

static struct ctl_table vm_table[] = {