get config (default: 4G)
ceph daemon mds.<mds-id> config get mds_cache_memory_limit
ceph daemon /var/run/ceph/<fsid>/<mds-id> config get mds_cache_memory_limit
ceph tell mds.storefs-a config show |grep mds_cache_memory_limit
set config on the fly not persistent (to 64 GB)
ceph daemon mds.<mds.id> config set mds_cache_memory_limit 68719476736
ceph daemon /var/run/ceph/<fsid>/<mds-id> set mds_cache_memory_limit 68719476736
ceph tell mds.storefs-a injectargs --mds_cache_memory_limit 68719476736
persist config ( to 64 GB)
ceph config set mds mds_cache_memory_limit 68719476736