It looks like that the org.nuxeo.ecm.core.storage.sql.ra.ConnectionImpl#queryResults set is not cleaned and create leak.
This can be seen in heap histo:
34: 192972 10806432 org.nuxeo.ecm.core.storage.sql.jdbc.ResultSetQueryResult ... 37: 192972 7718880 org.nuxeo.ecm.core.storage.sql.SessionImpl$QueryResultContextException