Code review markups.

routetable/route_table.go

@@ -357,6 +357,10 @@ func (r *RouteTable) syncRoutesForLink(ifaceName string) error {
 
 // startConntrackDeletion starts the deletion of conntrack entries for the given CIDR in the background.  Pending
 // deletions are tracked in the pendingConntrackCleanups map so we can block waiting for them later.
+//
+// It's important to do the conntrack deletions in the background because scanning the conntrack
+// table is very slow if there are a lot of entries.  Previously, we did the deletion synchronously
+// but that led to lengthy Apply() calls on the critical path.
 func (r *RouteTable) startConntrackDeletion(ipAddr ip.Addr) {
 	log.WithField("ip", ipAddr).Debug("Starting goroutine to delete conntrack entries")
 	done := make(chan struct{})

routetable/route_table_test.go

@@ -116,8 +116,9 @@ var _ = Describe("RouteTable", func() {
 		})
 
 		Describe("with a slow conntrack deletion", func() {
+			const delay = 300 * time.Millisecond
 			BeforeEach(func() {
-				dataplane.ConntrackSleep = 30 * time.Millisecond
+				dataplane.ConntrackSleep = delay
 			})
 			It("should block a route add until conntrack finished", func() {
 				// Initial apply starts a background thread to delete
@@ -129,7 +130,7 @@ var _ = Describe("RouteTable", func() {
 				})
 				start := time.Now()
 				rt.Apply()
-				Expect(time.Since(start)).To(BeNumerically(">=", 30*time.Millisecond))
+				Expect(time.Since(start)).To(BeNumerically(">=", delay))
 			})
 			It("should not block an unrelated route add ", func() {
 				// Initial apply starts a background thread to delete
@@ -141,7 +142,7 @@ var _ = Describe("RouteTable", func() {
 				})
 				start := time.Now()
 				rt.Apply()
-				Expect(time.Since(start)).To(BeNumerically("<", 10*time.Millisecond))
+				Expect(time.Since(start)).To(BeNumerically("<", delay/2))
 			})
 		})