Unknow problem make innodb_buffer_pool_size useless in cluster environment

I’ve setup 2 servers in my cluster, but something strange happend.
I’ve tried to change innodb_buffer_pool_size this variable in 1G , 8G 10G ,enven make it comment out. My both server still use 13G memory.
Who can help me?

I copy my.cnf in the below:
[mysqld]
datadir = /Data/mysql/data
socket=/Data/mysql/mysql.sock
user=mysql
character-set-server = utf8
port = 3306

Disabling symbolic-links is recommended to prevent assorted security risks

symbolic-links=0
default-storage-engine=InnoDB
explicit_defaults_for_timestamp=true

character-set-server = utf8
sort_buffer_size = 4M
max_connections = 65535
join_buffer_size = 4M
#thread_concurrency=16
#InnoDB
innodb_data_file_path=ibdata1:2048M:autoextend
innodb_buffer_pool_size = 6G
innodb_log_buffer_size = 8M
innodb_log_file_size = 256M
innodb_log_files_in_group = 3
innodb_autoinc_lock_mode=2
innodb_additional_mem_pool_size = 32M
innodb_thread_concurrency=0
log-bin=/Data/mysql/binlog/bin-file.log
binlog_cache_size = 1M
binlog_format=ROW
max_binlog_size=256M
max_binlog_cache_size=50M

log-error=/Data/mysql/mysqld_error.log

wsrep_provider=/usr/lib64/libgalera_smm.so
wsrep_cluster_address=gcomm://172.168.3.57,172.168.3.58
wsrep_node_address=172.168.3.57
wsrep_sst_method=xtrabackup-v2
wsrep_cluster_name=test.cluster
wsrep_sst_auth=“sstuser:s3cret”

[mysqld_safe]
pid-file=/Data/mysql/mysqld.pid

socket=/Data/mysql/mysql.sock

[client]
socket=/Data/mysql/mysql.sock

I don’t think I understand the problem - what is the error you get? What does it mean “useless”?