!323 [OLK-5.10] sched: Introduce priority load balance for CFS

Merge Pull Request from: @zhangsong234 
 
euleros inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5HF3M
CVE: NA

Add new sysctl interface:
`/proc/sys/kernel/sched_prio_load_balance_enabled`

 0: default behavior
 1: enable priority load balance for qos scheduler

For tasks co-location with qos scheduler, when CFS do load balance,
it is reasonable to prefer migrating online(Latency Sensitive) tasks.
So the CFS load balance can be changed to below:

1) `cfs_tasks` list is owned by online tasks.
2) Add new `cfs_offline_tasks` list which is owned by offline tasks.
3) Prefer to migrate the online tasks of `cfs_tasks` list to dst rq.

In the scenario of hyperthread interference, if the smt expeller feature
enabled, CPU A and CPU B are two hyperthreads on a physical core,
CPU A runs online tasks while CPU B only has offline tasks, The offline
tasks on CPU B are expelled by the online tasks on CPU A and cannot be
scheduled. However, when load balance is triggered, before CPU B can
migrate some online tasks from CPU A, the load on the two cpus is already
balanced. As a result, CPU B cannot run online tasks and online tasks
cannot be evenly distributed among different cpus. 
 
Link:https://gitee.com/openeuler/kernel/pulls/323

 

Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Zucheng Zheng <zhengzucheng@huawei.com>
Reviewed-by: Liu Chao <liuchao173@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>