sched: tweak the sched_runtime_limit tunable

Michael Gerdau reported reniced task CPU usage weirdnesses.
Such symptoms can be caused by limit underruns so double the
sched_runtime_limit.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -4923,7 +4923,7 @@ static inline void sched_init_granularity(void)
 	if (sysctl_sched_granularity > gran_limit)
 		sysctl_sched_granularity = gran_limit;
 
-	sysctl_sched_runtime_limit = sysctl_sched_granularity * 4;
+	sysctl_sched_runtime_limit = sysctl_sched_granularity * 8;
 	sysctl_sched_wakeup_granularity = sysctl_sched_granularity / 2;
 }