XANMOD: sched/core: Add yield_type sysctl to reduce or disable sched_…

…yield

[1] hamadmarri/cacule-cpu-scheduler#35

Signed-off-by: Alexandre Frade <kernel@xanmod.org>

kernel/sched/core.c

@@ -138,6 +138,14 @@ __read_mostly int sysctl_resched_latency_warn_ms = 100;
 __read_mostly int sysctl_resched_latency_warn_once = 1;
 #endif /* CONFIG_SCHED_DEBUG */
 
+/*
+ * Choose the yield level that will perform.
+ * 0: No yield.
+ * 1: Yield only to better priority/deadline tasks.
+ * 2: Re-queue current tasks. (default CFS)
+ */
+__read_mostly int sysctl_sched_yield_type = 0;
+
 /*
  * Number of tasks to iterate in a single balance run.
  * Limited because this is done with IRQs disabled.
@@ -8241,10 +8249,15 @@ static void do_sched_yield(void)
 	struct rq_flags rf;
 	struct rq *rq;
 
+	if (!sysctl_sched_yield_type)
+		return;
+
 	rq = this_rq_lock_irq(&rf);
 
 	schedstat_inc(rq->yld_count);
-	current->sched_class->yield_task(rq);
+
+	if (sysctl_sched_yield_type > 1)
+		current->sched_class->yield_task(rq);
 
 	preempt_disable();
 	rq_unlock_irq(rq, &rf);

kernel/sysctl.c

@@ -91,6 +91,7 @@ static const int six_hundred_forty_kb = 640 * 1024;
 #endif
 
 
+extern int sysctl_sched_yield_type;
 static const int ngroups_max = NGROUPS_MAX;
 static const int cap_last_cap = CAP_LAST_CAP;
 
@@ -1612,6 +1613,15 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+	{
+		.procname	= "yield_type",
+		.data		= &sysctl_sched_yield_type,
+		.maxlen		= sizeof (int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO,
+	},
 #ifdef CONFIG_USER_NS
 	{
 		.procname	= "unprivileged_userns_clone",