diff --git a/neutron/agent/linux/dhcp.py b/neutron/agent/linux/dhcp.py
index 55509cb84b2..f594b775c0f 100644
--- a/neutron/agent/linux/dhcp.py
+++ b/neutron/agent/linux/dhcp.py
@@ -483,6 +483,8 @@ class Dnsmasq(DhcpLocalProcess):
         LOG.debug('Building host file: %s', filename)
         dhcp_enabled_subnet_ids = [s.id for s in self.network.subnets
                                    if s.enable_dhcp]
+        # NOTE(ihrachyshka): the loop should not log anything inside it, to
+        # avoid potential performance drop when lots of hosts are dumped
         for (port, alloc, hostname, name) in self._iter_hosts():
             if not alloc:
                 if getattr(port, 'extra_dhcp_opts', False):
diff --git a/neutron/tests/unit/agent/linux/test_dhcp.py b/neutron/tests/unit/agent/linux/test_dhcp.py
index 09a91a7caa5..fca35c1bb8b 100644
--- a/neutron/tests/unit/agent/linux/test_dhcp.py
+++ b/neutron/tests/unit/agent/linux/test_dhcp.py
@@ -1403,6 +1403,16 @@ class TestDnsmasq(TestBase):
                                   'bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb'],
                                  sorted(result))
 
+    def test__output_hosts_file_log_only_twice(self):
+        dm = self._get_dnsmasq(FakeDualStackNetworkSingleDHCP())
+        with mock.patch.object(dhcp.LOG, 'process') as process:
+            process.return_value = ('fake_message', {})
+            dm._output_hosts_file()
+        # The method logs twice, at the start of and the end. There should be
+        # no other logs, no matter how many hosts there are to dump in the
+        # file.
+        self.assertEqual(2, process.call_count)
+
     def test_only_populates_dhcp_enabled_subnets(self):
         exp_host_name = '/dhcp/eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee/host'
         exp_host_data = ('00:00:80:aa:bb:cc,host-192-168-0-2.openstacklocal,'