outlet/routing: fix lookup benchmark

The lookup benchmark was incorrect. When looking up a large number of
prefixes on each loop, b.Loop() calibrate on a larger and less precise
value than if it were measuring only one lookup where it would iterate
more to get a precise timing.

The problem may also exist for the insertion benchmark, but it's
difficult to do only one insertion per loop, as after many iterations,
there is nothing more we can insert. I suppose BART's author is not
trying to benchmark insertions because of this.

See https://github.com/akvorado/akvorado/pull/2040 and
https://github.com/gaissmai/bart/issues/351#issuecomment-3428806758.

orchestrator/clickhouse/networks_test.go

@@ -187,9 +187,10 @@ func BenchmarkNetworks(b *testing.B) {
 	<-c.networksCSVReady
 
 	for b.Loop() {
-		if err := c.networksCSVRefresh(); err != nil {
-			b.Fatalf("networksCSVRefresh() error:\n%+v", err)
+		err = c.networksCSVRefresh()
 	}
+	if err != nil {
+		b.Fatalf("networksCSVRefresh() error:\n%+v", err)
 	}
 	b.ReportMetric(0, "ns/op")
 	b.ReportMetric(float64(b.Elapsed())/float64(b.N)/1_000_000, "ms/op")

outlet/routing/provider/bmp/prefixes_test.go

@@ -204,18 +204,6 @@ func TestRandomRealWorldRoutes4Distribution(t *testing.T) {
 	}
 }
 
-func BenchmarkRandomRealWorldRoutes4(b *testing.B) {
-	prng1 := rand.New(rand.NewSource(1))
-	prng2 := rand.New(rand.NewSource(2))
-	for b.Loop() {
-		for route := range randomRealWorldRoutes4(prng1, prng2, 1000) {
-			_ = route
-		}
-	}
-	b.ReportMetric(0, "ns/op")
-	b.ReportMetric(float64(b.Elapsed())/float64(b.N)/1000, "ns/route")
-}
-
 func BenchmarkRIBInsertion(b *testing.B) {
 	for _, routes := range []int{1_000, 10_000, 100_000} {
 		for _, peers := range []int{1, 2, 5} {
@@ -283,7 +271,13 @@ func BenchmarkRIBInsertion(b *testing.B) {
 }
 
 func BenchmarkRIBLookup(b *testing.B) {
-	for _, routes := range []int{1_000, 10_000, 100_000} {
+	for _, routes := range []int{1_000, 10_000, 100_000, 1_000_000} {
+		prng1 := rand.New(rand.NewSource(10))
+		prng2 := rand.New(rand.NewSource(0))
+		randomPrefixes := []randomRoute{}
+		for r := range randomRealWorldRoutes4(prng1, prng2, routes/10) {
+			randomPrefixes = append(randomPrefixes, r)
+		}
 		for _, peers := range []int{1, 2, 5} {
 			name := fmt.Sprintf("%d routes, %d peers", routes, peers)
 
@@ -317,19 +311,11 @@ func BenchmarkRIBLookup(b *testing.B) {
 					}
 				}
 
-				prng1 = rand.New(rand.NewSource(10))
-				lookups := 0
-				randomPrefixes := []randomRoute{}
-				for r := range randomRealWorldRoutes4(prng1, prng2[0], routes/10) {
-					randomPrefixes = append(randomPrefixes, r)
-				}
 				for b.Loop() {
-					for _, r := range randomPrefixes {
-						_, _ = rib.tree.Lookup(netip.AddrFrom16(r.Prefix.Addr().As16()))
-						lookups++
+					ip4 := randomPrefixes[b.N%len(randomPrefixes)].Prefix.Addr()
+					_, _ = rib.tree.Lookup(ip4)
 				}
-				}
-				b.ReportMetric(float64(b.Elapsed())/float64(lookups), "ns/op")
+				b.ReportMetric(float64(b.Elapsed())/float64(b.N), "ns/op")
 			})
 		}
 	}