Merge pull request #104806 from MikeSpreitzer/set-g-to-3ms

Change execution duration guess from 1 minute to 3 milliseconds

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/fifo_list.go

@@ -45,6 +45,9 @@ type fifo interface {
 	// Dequeue pulls out the oldest request from the list.
 	Dequeue() (*request, bool)
 
+	// Peek returns the oldest request without removing it.
+	Peek() (*request, bool)
+
 	// Length returns the number of requests in the list.
 	Length() int
 
@@ -97,18 +100,28 @@ func (l *requestFIFO) Enqueue(req *request) removeFromFIFOFunc {
 }
 
 func (l *requestFIFO) Dequeue() (*request, bool) {
+	return l.getFirst(true)
+}
+
+func (l *requestFIFO) Peek() (*request, bool) {
+	return l.getFirst(false)
+}
+
+func (l *requestFIFO) getFirst(remove bool) (*request, bool) {
 	e := l.Front()
 	if e == nil {
 		return nil, false
 	}
 
+	if remove {
 		defer func() {
 			l.Remove(e)
 			e.Value = nil
 		}()
+	}
 
 	request, ok := e.Value.(*request)
-	if ok {
+	if remove && ok {
 		l.seatsSum -= request.Seats()
 	}
 	return request, ok

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/queueset.go

@@ -77,7 +77,7 @@ type queueSetCompleter struct {
 // locking.
 type queueSet struct {
 	clock                   eventclock.Interface
-	estimatedServiceTime float64
+	estimatedServiceSeconds float64
 	obsPair                 metrics.TimedObserverPair
 
 	promiseFactory promiseFactory
@@ -171,7 +171,7 @@ func (qsc *queueSetCompleter) Complete(dCfg fq.DispatchingConfig) fq.QueueSet {
 	if qs == nil {
 		qs = &queueSet{
 			clock:                   qsc.factory.clock,
-			estimatedServiceTime: 60,
+			estimatedServiceSeconds: 0.003,
 			obsPair:                 qsc.obsPair,
 			qCfg:                    qsc.qCfg,
 			virtualTime:             0,
@@ -642,8 +642,8 @@ func (qs *queueSet) dispatchLocked() bool {
 			qs.qCfg.Name, request.startTime.Format(nsTimeFmt), qs.virtualTime, request.descr1, request.descr2,
 			request.workEstimate, queue.index, queue.virtualStart, queue.requests.Length(), queue.requestsExecuting, queue.seatsInUse, qs.totSeatsInUse)
 	}
-	// When a request is dequeued for service -> qs.virtualStart += G
+	// When a request is dequeued for service -> qs.virtualStart += G * width
-	queue.virtualStart += qs.estimatedServiceTime * float64(request.Seats())
+	queue.virtualStart += qs.estimatedServiceSeconds * float64(request.Seats())
 	request.decision.Set(decisionExecute)
 	return ok
 }
@@ -686,29 +686,14 @@ func (qs *queueSet) selectQueueLocked() *queue {
 	for range qs.queues {
 		qs.robinIndex = (qs.robinIndex + 1) % nq
 		queue := qs.queues[qs.robinIndex]
-		if queue.requests.Length() != 0 {
+		oldestWaiting, _ := queue.requests.Peek()
+		if oldestWaiting != nil {
 			sMin = math.Min(sMin, queue.virtualStart)
 			sMax = math.Max(sMax, queue.virtualStart)
-			estimatedWorkInProgress := qs.estimatedServiceTime * float64(queue.seatsInUse)
+			estimatedWorkInProgress := qs.estimatedServiceSeconds * float64(queue.seatsInUse)
 			dsMin = math.Min(dsMin, queue.virtualStart-estimatedWorkInProgress)
 			dsMax = math.Max(dsMax, queue.virtualStart-estimatedWorkInProgress)
-			// the finish R of the oldest request is:
+			currentVirtualFinish := queue.virtualStart + qs.estimatedServiceSeconds*float64(oldestWaiting.Seats())
-			//   start R + G
-			// we are not taking the width of the request into account when
-			// we calculate the virtual finish time of the request because
-			// it can starve requests with smaller wdith in other queues.
-			//
-			// so let's draw an example of the starving scenario:
-			//  - G=60 (estimated service time in seconds)
-			//  - concurrency limit=2
-			//  - we have two queues, q1 and q2
-			//  - q1 has an infinite supply of requests with width W=1
-			//  - q2 has one request waiting in the queue with width W=2
-			//  - start R for both q1 and q2 are at t0
-			//  - requests complete really fast, S=1ms on q1
-			// in this scenario we will execute roughly 60,000 requests
-			// from q1 before we pick the request from q2.
-			currentVirtualFinish := queue.virtualStart + qs.estimatedServiceTime
 			klog.V(11).InfoS("Considering queue to dispatch", "queueSet", qs.qCfg.Name, "queue", qs.robinIndex, "finishR", currentVirtualFinish)
 			if currentVirtualFinish < minVirtualFinish {
 				minVirtualFinish = currentVirtualFinish
@@ -718,12 +703,7 @@ func (qs *queueSet) selectQueueLocked() *queue {
 		}
 	}
 
-	// TODO: add a method to fifo that lets us peek at the oldest request
+	oldestReqFromMinQueue, _ := minQueue.requests.Peek()
-	var oldestReqFromMinQueue *request
-	minQueue.requests.Walk(func(r *request) bool {
-		oldestReqFromMinQueue = r
-		return false
-	})
 	if oldestReqFromMinQueue == nil {
 		// This cannot happen
 		klog.ErrorS(errors.New("selected queue is empty"), "Impossible", "queueSet", qs.qCfg.Name)
@@ -755,7 +735,7 @@ func (qs *queueSet) selectQueueLocked() *queue {
 	// queue here. if the last start R (excluded estimated cost)
 	// falls behind the global virtual time, we update the latest virtual
 	// start by: <latest global virtual time> + <previously estimated cost>
-	previouslyEstimatedServiceTime := float64(minQueue.seatsInUse) * qs.estimatedServiceTime
+	previouslyEstimatedServiceTime := float64(minQueue.seatsInUse) * qs.estimatedServiceSeconds
 	if qs.virtualTime > minQueue.virtualStart-previouslyEstimatedServiceTime {
 		// per-queue virtual time should not fall behind the global
 		minQueue.virtualStart = qs.virtualTime + previouslyEstimatedServiceTime
@@ -853,7 +833,7 @@ func (qs *queueSet) finishRequestLocked(r *request) {
 
 		// When a request finishes being served, and the actual service time was S,
 		// the queue’s start R is decremented by (G - S)*width.
-		r.queue.virtualStart -= (qs.estimatedServiceTime - S) * float64(r.Seats())
+		r.queue.virtualStart -= (qs.estimatedServiceSeconds - S) * float64(r.Seats())
 	}
 }
 

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/queueset_test.go

@@ -1034,7 +1034,7 @@ func TestTotalRequestsExecutingWithPanic(t *testing.T) {
 }
 
 func TestSelectQueueLocked(t *testing.T) {
-	var G float64 = 60
+	var G float64 = 0.003
 	tests := []struct {
 		name                    string
 		robinIndex              int
@@ -1087,7 +1087,7 @@ func TestSelectQueueLocked(t *testing.T) {
 			robinIndexExpected:    []int{0},
 		},
 		{
-			name:             "width > 1, seats are available for request with the least finish time, queue is picked",
+			name:             "width > 1, seats are available for request with the least finish R, queue is picked",
 			concurrencyLimit: 50,
 			totSeatsInUse:    25,
 			robinIndex:       -1,
@@ -1110,7 +1110,7 @@ func TestSelectQueueLocked(t *testing.T) {
 			robinIndexExpected:    []int{1},
 		},
 		{
-			name:             "width > 1, seats are not available for request with the least finish time, queue is not picked",
+			name:             "width > 1, seats are not available for request with the least finish R, queue is not picked",
 			concurrencyLimit: 50,
 			totSeatsInUse:    26,
 			robinIndex:       -1,
@@ -1165,9 +1165,10 @@ func TestSelectQueueLocked(t *testing.T) {
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			qs := &queueSet{
-				estimatedServiceTime: G,
+				estimatedServiceSeconds: G,
 				robinIndex:              test.robinIndex,
 				totSeatsInUse:           test.totSeatsInUse,
+				qCfg:                    fq.QueuingConfig{Name: "TestSelectQueueLocked/" + test.name},
 				dCfg: fq.DispatchingConfig{
 					ConcurrencyLimit: test.concurrencyLimit,
 				},

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/types.go

@@ -76,13 +76,14 @@ type request struct {
 // queue is an array of requests with additional metadata required for
 // the FQScheduler
 type queue struct {
-	// The requests are stored in a FIFO list.
+	// The requests not yet executing in the real world are stored in a FIFO list.
 	requests fifo
 
 	// virtualStart is the "virtual time" (R progress meter reading) at
 	// which the next request will be dispatched in the virtual world.
 	virtualStart float64
 
+	// requestsExecuting is the count in the real world
 	requestsExecuting int
 	index             int