diff -Nru neutron-16.4.2/debian/changelog neutron-16.4.2/debian/changelog
--- neutron-16.4.2/debian/changelog	2022-07-06 03:50:56.000000000 +0800
+++ neutron-16.4.2/debian/changelog	2022-09-08 06:59:57.000000000 +0800
@@ -1,3 +1,10 @@
+neutron (2:16.4.2-0ubuntu4) focal; urgency=medium
+
+  * d/defer-flow-deletion-in-openvswitch-firewall.patch 
+  Defer flow deletion in openvswitch firewall (LP: #1975674)
+
+ -- Zhang Hua <joshua.zhang@canonical.com>  Thu, 08 Sep 2022 06:59:57 +0800
+
 neutron (2:16.4.2-0ubuntu3) focal; urgency=medium
 
   * d/p/partially-revert-do-not-link-up-ha-router-gateway-in.patch:
diff -Nru neutron-16.4.2/debian/patches/defer-flow-deletion-in-openvswitch-firewall.patch neutron-16.4.2/debian/patches/defer-flow-deletion-in-openvswitch-firewall.patch
--- neutron-16.4.2/debian/patches/defer-flow-deletion-in-openvswitch-firewall.patch	1970-01-01 08:00:00.000000000 +0800
+++ neutron-16.4.2/debian/patches/defer-flow-deletion-in-openvswitch-firewall.patch	2022-09-08 06:59:50.000000000 +0800
@@ -0,0 +1,41 @@
+From 1a01d0e66a430d6716cf969facb15f626f0ed1a6 Mon Sep 17 00:00:00 2001
+From: Henning Eggers <henning@eggers.name>
+Date: Wed, 25 May 2022 11:17:43 +0200
+Subject: [PATCH] Defer flow deletion in openvswitch firewall
+
+Reduces the deletion time of conjunction flows on hypervisors
+where virtual machines reside which are part of a security
+group that has remote security groups as target which contain
+thousands of ports.
+
+Without deferred deletion the agent will call ovs-ofctl several
+hundred times in succession, during this time the agent will
+block any new vm creation or neutron port modifications on this
+hypervisor.
+
+This patch has been tested using a single network with a single
+vm with a security group that points to a remote security group
+with 2000 ports.
+
+During testing without the patch, the iteration time for deletion
+was at around 500 seconds. After adding the patch to the l2 agent
+on the test environment the same deletion time went down to
+4 seconds.
+
+Closes-Bug: #1975674
+Change-Id: I46b1fe94b2e358f7f4b2cd4943a74ebaf84f51b8
+(cherry picked from commit e09b128f416a809cd7734aba8ab52220ea01b2e2)
+(cherry picked from commit 30ef996f8aa0b0bc57a280690871f1081946ffee)
+Signed-off-by: Zhang Hua <joshua.zhang@canonical.com>
+---
+ neutron/agent/linux/openvswitch_firewall/firewall.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- neutron-16.4.2.orig/neutron/agent/linux/openvswitch_firewall/firewall.py
++++ neutron-16.4.2/neutron/agent/linux/openvswitch_firewall/firewall.py
+@@ -1553,4 +1553,4 @@ class OVSFirewallDriver(firewall.Firewal
+             # will not match with the ip flow's cookie so OVS won't actually
+             # delete the flow
+             flow['cookie'] = ovs_lib.COOKIE_ANY
+-            self._delete_flows(deferred=False, **flow)
++            self._delete_flows(**flow)
diff -Nru neutron-16.4.2/debian/patches/series neutron-16.4.2/debian/patches/series
--- neutron-16.4.2/debian/patches/series	2022-07-06 03:50:56.000000000 +0800
+++ neutron-16.4.2/debian/patches/series	2022-09-08 06:59:07.000000000 +0800
@@ -9,3 +9,4 @@
 lp1975594-0006-Use-Port_Binding-up-column-to-set-Neutron-port-statu.patch
 lp1975594-0007-support-SB-OVSDB-connections-to-non-leader-servers.patch
 lp1975594-0008-fix-setting-table-monitoring-conditions.patch
+defer-flow-deletion-in-openvswitch-firewall.patch