sched/fair: remove the DOUBLE_TICK feature

The patch "5e963f2bd46 sched/fair: Commit to EEVDF"
removed the code following the DOUBLE_TICK:
	-
	-       if (!sched_feat(EEVDF) && cfs_rq->nr_running > 1)
	-               check_preempt_tick(cfs_rq, curr);

The DOUBLE_TICK feature becomes dead code now, so remove it.

Signed-off-by: Huang Shijie <shijie@os.amperecomputing.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: "Christoph Lameter (Ampere)" <cl@linux.com>
Reviewed-by: Vishal Chourasia <vishalc@linux.ibm.com>
Link: https://lore.kernel.org/r/20241001065451.10356-1-shijie@os.amperecomputing.com

Author: HuangShijie2024

kernel/sched/fair.c

@@ -5680,12 +5680,6 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 		resched_curr(rq_of(cfs_rq));
 		return;
 	}
-	/*
-	 * don't let the period tick interfere with the hrtick preemption
-	 */
-	if (!sched_feat(DOUBLE_TICK) &&
-			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
-		return;
 #endif
 }
 

kernel/sched/features.h

@@ -56,7 +56,6 @@ 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