List users is too slow when existing amount of ldap users

[jun923.gu]

We encounter the situation that query users is too slow when existing amount of LDAP users. We create a domain and config LDAP into the domain, there are 20000 users data in the LDAP server. When we query users in the domain, we spend about 20 seconds to return all users in the domain.
[root@vm /]# time openstack user list --domain f50ccdfe4263414299271bdd61b42e65|wc -l
20004

real 0m20.445s
user 0m6.018s
sys 0m0.575s
We refer the following link: https://bugs.launchpad.net/keystone/+bug/1582585 and found our's code have including the patches. So we think it's necessary to optimize the performance of querying users again.