fix(QOSSort): refine queue sorting logic by adding inqueue timestamp

pkg/qos/queue_sort.go

@@ -41,11 +41,19 @@ func (pl *Sort) Name() string {
 
 // Less is the function used by the activeQ heap algorithm to sort pods.
 // It sorts pods based on their priorities. When the priorities are equal, it uses
-// the Pod QoS classes to break the tie.
+// the Pod QoS classes to break the tie. If both the priority and QoS class are equal,
+// it uses PodQueueInfo.timestamp.
 func (*Sort) Less(pInfo1, pInfo2 *framework.QueuedPodInfo) bool {
 	p1 := corev1helpers.PodPriority(pInfo1.Pod)
 	p2 := corev1helpers.PodPriority(pInfo2.Pod)
-	return (p1 > p2) || (p1 == p2 && compQOS(pInfo1.Pod, pInfo2.Pod))
+
+	if p1 != p2 {
+		return p1 > p2
+	}
+	if compQOS(pInfo1.Pod, pInfo2.Pod) {
+		return true
+	}
+	return pInfo1.Timestamp.Before(pInfo2.Timestamp)
 }
 
 func compQOS(p1, p2 *v1.Pod) bool {

pkg/qos/queue_sort_test.go

@@ -18,6 +18,7 @@ package qos
 
 import (
 	"testing"
+	"time"
 
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
@@ -31,6 +32,8 @@ func createPodInfo(pod *v1.Pod) *framework.PodInfo {
 }
 
 func TestSortLess(t *testing.T) {
+	t1 := time.Now()
+	t2 := t1.Add(time.Second)
 	tests := []struct {
 		name   string
 		pInfo1 *framework.QueuedPodInfo
@@ -117,6 +120,18 @@ func TestSortLess(t *testing.T) {
 			},
 			want: true,
 		},
+		{
+			name: "both p1 and p2 are Guaranteed, but p1 is added to schedulingQ earlier than p2",
+			pInfo1: &framework.QueuedPodInfo{
+				PodInfo:   createPodInfo(makePod("p1", 0, getResList("100m", "100Mi"), getResList("100m", "100Mi"))),
+				Timestamp: t1,
+			},
+			pInfo2: &framework.QueuedPodInfo{
+				PodInfo:   createPodInfo(makePod("p2", 0, getResList("100m", "100Mi"), getResList("100m", "100Mi"))),
+				Timestamp: t2,
+			},
+			want: true,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {