Comment 1 for bug 1497219

strace analysis shows that the issue is caused by a single SQL query:

SELECT routerports.router_id AS routerports_router_id, routerports.port_id AS routerports_port_id, routerports.port_type AS routerports_port_type, ipallocations_1.port_id AS ipallo
cations_1_port_id, ipallocations_1.ip_address AS ipallocations_1_ip_address, ipallocations_1.subnet_id AS ipallocations_1_subnet_id, ipallocations_1.network_id AS ipallocations_1_network_id, ports_1.tenant
_id AS por....

which has list of parameters with ~1000 items

the response size is about 2G, after reading the response process starts to call mmap() retrieving more memory.
overall the processing takes several minutes.

Neutron function that matches query pattern is l3_db.get_sync_interfaces()