sched/fair: Provide idle search schedstats

maillist inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8PIYZ
CVE: NA

Reference: https://lore.kernel.org/lkml/1541767840-93588-11-git-send-email-steven.sistare@oracle.com/



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Add schedstats to measure the effectiveness of searching for idle CPUs
and stealing tasks.  This is a temporary patch intended for use during
development only.  SCHEDSTAT_VERSION is bumped to 16, and the following
fields are added to the per-CPU statistics of /proc/schedstat:

field 10: # of times select_idle_sibling "easily" found an idle CPU --
          prev or target is idle.
field 11: # of times select_idle_sibling searched and found an idle cpu.
field 12: # of times select_idle_sibling searched and found an idle core.
field 13: # of times select_idle_sibling failed to find anything idle.
field 14: time in nanoseconds spent in functions that search for idle
          CPUs and search for tasks to steal.
field 15: # of times an idle CPU steals a task from another CPU.
field 16: # of times try_steal finds overloaded CPUs but no task is
           migratable.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Signed-off-by: Cheng Yu <serein.chengyu@huawei.com>