scheduler: Add runtime knob sysctl_sched_cluster

kunpeng inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5W44S
CVE: NA

Reference: https://lore.kernel.org/lkml/cover.1638563225.git.tim.c.chen@linux.intel.com/



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Allow run time configuration of the scheduler to use cluster
scheduling.  Configuration can be changed via the sysctl variable
/proc/sys/kernel/sched_cluster. Setting it to 1 enable cluster
scheduling and setting it to 0 turns it off.

Cluster scheduling should benefit independent tasks by load balancing
them between clusters.  It reaps the most benefit when the system's CPUs
are not fully busy, so we can spread the tasks out between the clusters to
reduce contention on cluster resource (e.g. L2 cache).

However, if the system is expected to operate close to full utilization,
the system admin could turn this feature off so as not to incur
extra load balancing overhead between the cluster domains.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Jie Liu <liujie375@h-partners.com>