Lustre 1.6 Operations Manual

20.2.9 Locking
/proc/fs/lustre/ldlm/ldlm/namespaces//lru_size
The lru_size parameter is used to control the number of client-side locks in an LRU
queue. LRU size is dynamic, based on load. This optimizes the number of locks
available to nodes that have different workloads (e.g., login/build nodes vs.
compute nodes vs. backup nodes).
The total number of locks available is a function of the server’s RAM. The maximum
is 50 locks/MB. If there is too much memory pressure, then the LRU size is shrunk.
■ To enable automatic LRU sizing, set the lru_size parameter to 0. In this case, the
lru_size parameter shows the current number of locks being used on the export.
■ To specify a maximum number of locks, set the lru_size parameter to a value > 0
(former numbers are okay, 100 * CPU_NR). We recommend that you only increase
the LRU size on a few login nodes where users access the file system interactively.
The following command can be used to clear the LRU on a single client, and as a
result flush client cache, without changing the lru_size value:
$ lctl set_param ldlm.namespaces..lru_size=clear
If you shrink the LRU size below the number of existing unused locks, then the
unused locks are canceled immediately. Use echo clear to cancel all locks without
changing the value.
20-24 Lustre 1.6 Operations Manual • September 2008