elaborate comments

Author: sanposhiho

pkg/scheduler/internal/queue/scheduling_queue.go

@@ -1194,8 +1194,14 @@ func (p *PriorityQueue) movePodsToActiveOrBackoffQueue(logger klog.Logger, podIn
 
 	activated := false
 	for _, pInfo := range podInfoList {
-		// Since there may be many gated pods and they will not move from the
-		// unschedulable pool, we skip calling the expensive isPodWorthRequeueing.
+		// Scheduling-gated Pods never get schedulable with any events,
+		// except the Pods themselves got updated, which isn't handled by movePodsToActiveOrBackoffQueue.
+		// So, here we skip them early here so that they don't go through isPodWorthRequeuing,
+		// which isn't fast enough when the number of scheduling-gated Pods in unschedulablePods is large.
+		//
+		// Note that we cannot skip all pInfo.Gated Pods here
+		// because PreEnqueue plugins apart from the scheduling gate plugin may change the gating status
+		// with these events.
 		if pInfo.Gated && pInfo.UnschedulablePlugins.Has(names.SchedulingGates) {
 			continue
 		}