This is a minor suggestion to improve teh performance of the LDAP import when it is taking place as the result of synchronisation when login in via OpenSSO, i.e. when open.sso.ldap.import.enabled=true.
Basically, the current code simply re-adds the user to all groups listed from LDAP and those that they are already in which are not managed by LDAP. Each time the user is added to the group, a whole series of database operations take place. The suggested code change results in the user only being added to those grops that they are not already a member of and attempts to reduce the number of iterations to achieve this. The change is in com.liferay.portal.securit.ldap.PortalLDAPImporterImpl.java - see the attached SVN patch.