perf: preallocate slices in route processing (#7041)

* perf: preallocate slices in route processing

Signed-off-by: Arko Dasgupta <arko@tetrate.io>

* use index

Signed-off-by: Arko Dasgupta <arko@tetrate.io>

Author: arkodg

internal/gatewayapi/contexts.go

@@ -78,8 +78,12 @@ type ListenerContext struct {
 }
 
 func (l *ListenerContext) SetSupportedKinds(kinds ...gwapiv1.RouteGroupKind) {
-	l.gateway.Status.Listeners[l.listenerStatusIdx].SupportedKinds = make([]gwapiv1.RouteGroupKind, 0, len(kinds))
-	l.gateway.Status.Listeners[l.listenerStatusIdx].SupportedKinds = append(l.gateway.Status.Listeners[l.listenerStatusIdx].SupportedKinds, kinds...)
+	if len(kinds) > 0 {
+		l.gateway.Status.Listeners[l.listenerStatusIdx].SupportedKinds = make([]gwapiv1.RouteGroupKind, len(kinds))
+		copy(l.gateway.Status.Listeners[l.listenerStatusIdx].SupportedKinds, kinds)
+	} else {
+		l.gateway.Status.Listeners[l.listenerStatusIdx].SupportedKinds = []gwapiv1.RouteGroupKind{}
+	}
 }
 
 func (l *ListenerContext) IncrementAttachedRoutes() {

internal/gatewayapi/helpers.go

@@ -591,9 +591,9 @@ func getPolicyTargetRefs[T client.Object](policy egv1a1.PolicyTargetReferences,
 	slices.SortFunc(selectorsList, func(i, j targetRefWithTimestamp) int {
 		return i.CreationTimestamp.Compare(j.CreationTimestamp.Time)
 	})
-	ret := []gwapiv1a2.LocalPolicyTargetReferenceWithSectionName{}
-	for _, v := range selectorsList {
-		ret = append(ret, v.LocalPolicyTargetReferenceWithSectionName)
+	ret := make([]gwapiv1a2.LocalPolicyTargetReferenceWithSectionName, len(selectorsList))
+	for i, v := range selectorsList {
+		ret[i] = v.LocalPolicyTargetReferenceWithSectionName
 	}
 	// Plain targetRefs in the policy don't have an associated creation timestamp, but can still refer
 	// to targets that were already found via the selectors. Only add them to the returned list if

internal/gatewayapi/route.go

@@ -212,11 +212,11 @@ func (t *Translator) processHTTPRouteRules(httpRoute *HTTPRouteContext, parentRe
 		}
 
 		destName := irRouteDestinationName(httpRoute, ruleIdx)
-		allDs := []*ir.DestinationSetting{}
+		allDs := make([]*ir.DestinationSetting, 0, len(rule.BackendRefs))
 		failedProcessDestination := false
 		hasDynamicResolver := false
 		backendRefNames := make([]string, len(rule.BackendRefs))
-		backendCustomRefs := []*ir.UnstructuredRef{}
+		backendCustomRefs := make([]*ir.UnstructuredRef, 0, len(rule.BackendRefs))
 		// process each backendRef, and calculate the destination settings for this rule
 		for i := range rule.BackendRefs {
 			settingName := irDestinationSettingName(destName, i)
@@ -664,7 +664,7 @@ func (t *Translator) processGRPCRouteRules(grpcRoute *GRPCRouteContext, parentRe
 		}
 
 		destName := irRouteDestinationName(grpcRoute, ruleIdx)
-		allDs := []*ir.DestinationSetting{}
+		allDs := make([]*ir.DestinationSetting, 0, len(rule.BackendRefs))
 		failedProcessDestination := false
 
 		backendRefNames := make([]string, len(rule.BackendRefs))

internal/gatewayapi/translator.go

@@ -202,22 +202,26 @@ func (t *Translator) Translate(resources *resource.Resources) (*TranslateResult,
 	// Process ClientTrafficPolicies
 	clientTrafficPolicies := t.ProcessClientTrafficPolicies(resources, acceptedGateways, xdsIR, infraIR)
 
-	// Process BackendTrafficPolicies
-	routes := []RouteContext{}
-	for _, h := range httpRoutes {
-		routes = append(routes, h)
+	routes := make([]RouteContext, len(httpRoutes)+len(grpcRoutes)+len(tlsRoutes)+len(tcpRoutes)+len(udpRoutes))
+	offset := 0
+	for i := range httpRoutes {
+		routes[offset+i] = httpRoutes[i]
 	}
-	for _, g := range grpcRoutes {
-		routes = append(routes, g)
+	offset += len(httpRoutes)
+	for i := range grpcRoutes {
+		routes[offset+i] = grpcRoutes[i]
 	}
-	for _, t := range tlsRoutes {
-		routes = append(routes, t)
+	offset += len(grpcRoutes)
+	for i := range tlsRoutes {
+		routes[offset+i] = tlsRoutes[i]
 	}
-	for _, t := range tcpRoutes {
-		routes = append(routes, t)
+	offset += len(tlsRoutes)
+	for i := range tcpRoutes {
+		routes[offset+i] = tcpRoutes[i]
 	}
-	for _, u := range udpRoutes {
-		routes = append(routes, u)
+	offset += len(tcpRoutes)
+	for i := range udpRoutes {
+		routes[offset+i] = udpRoutes[i]
 	}
 
 	// Process BackendTrafficPolicies