DLM uses several tables to manage, coordinate, and pass lock information between nodes in the cluster. Increasing the size of the DLM tables might increase performance. In Red Hat Enterprise Linux 6.1 and later, the default sizes of these tables have been increased, but you can manually increase them with the following commands:
echo 1024 > /sys/kernel/config/dlm/cluster/lkbtbl_size
echo 1024 > /sys/kernel/config/dlm/cluster/rsbtbl_size
echo 1024 > /sys/kernel/config/dlm/cluster/dirtbl_size
These commands are not persistent and will not survive a reboot, so you must add them to one of the startup scripts and you must execute them before mounting any GFS2 file systems, or the changes will be silently ignored.