ascend inclusion
category: perf
bugzilla: https://gitee.com/openeuler/kernel/issues/I4EUVI
CVE: NA

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We decide to remove sp_mutex thoroughly and use sp_group_sem instead.

Moreover, we use down_read(&spg->rw_lock) instead of down_write(), this
increases parallelism of sp_add_group_task(), especially when there are
many normal pages in the target sp_group.

Test: First a process is added into sp_group 1, then it calls sp_alloc()
to get 3.5G normal page memory and 5.5G hugepage memory. Then 30
processes are created and added to sp_group 1 concurrently. The result
is as follows.

without this patch: 15.0s
with this patch:    4.5s
gain:               70%
Tested-by: NTang Yizhou <tangyizhou@huawei.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NTang Yizhou <tangyizhou@huawei.com>
Reviewed-by: NKefeng  Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>