Update the logic to pick the best queue in P&F

Kubernetes-commit: 0ecc7ba311ab33b16c5d907ebb1120e3e51a947d

pkg/util/flowcontrol/fairqueuing/queueset/fifo_list.go

@@ -48,6 +48,10 @@ type fifo interface {
 	// Length returns the number of requests in the list.
 	Length() int
 
+	// Width returns the total width (number of seats) of requests
+	// in this list.
+	Width() int
+
 	// Walk iterates through the list in order of oldest -> newest
 	// and executes the specified walkFunc for each request in that order.
 	//
@@ -60,6 +64,8 @@ type fifo interface {
 // goroutines without additional locking or coordination.
 type requestFIFO struct {
 	*list.List
+
+	width int
 }
 
 func newRequestFIFO() fifo {
@@ -72,10 +78,20 @@ func (l *requestFIFO) Length() int {
 	return l.Len()
 }
 
+func (l *requestFIFO) Width() int {
+	return l.width
+}
+
 func (l *requestFIFO) Enqueue(req *request) removeFromFIFOFunc {
 	e := l.PushBack(req)
+	l.width += req.Seats()
+
 	return func() *request {
-		l.Remove(e)
+		if e.Value != nil {
+			l.Remove(e)
+			e.Value = nil
+			l.width -= req.Seats()
+		}
 		return req
 	}
 }
@@ -85,9 +101,16 @@ func (l *requestFIFO) Dequeue() (*request, bool) {
 	if e == nil {
 		return nil, false
 	}
-	defer l.Remove(e)
+
+	defer func() {
+		l.Remove(e)
+		e.Value = nil
+	}()
 
 	request, ok := e.Value.(*request)
+	if ok {
+		l.width -= request.Seats()
+	}
 	return request, ok
 }
 

pkg/util/flowcontrol/fairqueuing/queueset/fifo_list_test.go

@@ -20,6 +20,8 @@ import (
 	"math/rand"
 	"testing"
 	"time"
+
+	fcrequest "k8s.io/apiserver/pkg/util/flowcontrol/request"
 )
 
 func TestFIFOWithEnqueueDequeueSingleRequest(t *testing.T) {
@@ -148,6 +150,62 @@ func TestFIFOWithRemoveIsIdempotent(t *testing.T) {
 	verifyOrder(t, orderExpected, remainingRequests)
 }
 
+func TestFIFOWidth(t *testing.T) {
+	list := newRequestFIFO()
+
+	newRequest := func(width uint) *request {
+		return &request{width: fcrequest.Width{Seats: width}}
+	}
+	arrival := []*request{newRequest(1), newRequest(2), newRequest(3)}
+	removeFn := make([]removeFromFIFOFunc, 0)
+
+	width := 0
+	for i := range arrival {
+		removeFn = append(removeFn, list.Enqueue(arrival[i]))
+
+		width += i + 1
+		if list.Width() != width {
+			t.Errorf("Expected width: %d, but got: %d", width, list.Width())
+		}
+	}
+
+	for i := range removeFn {
+		removeFn[i]()
+
+		width -= i + 1
+		if list.Width() != width {
+			t.Errorf("Expected width: %d, but got: %d", width, list.Width())
+		}
+
+		// check idempotency
+		removeFn[i]()
+		if list.Width() != width {
+			t.Errorf("Expected width: %d, but got: %d", width, list.Width())
+		}
+	}
+
+	// Check second type of idempotency: Dequeue + removeFn.
+	for i := range arrival {
+		removeFn[i] = list.Enqueue(arrival[i])
+		width += i + 1
+	}
+
+	for i := range arrival {
+		if _, ok := list.Dequeue(); !ok {
+			t.Errorf("Unexpected failed dequeue: %d", i)
+		}
+		width -= i + 1
+		if list.Width() != width {
+			t.Errorf("Expected width: %d, but got: %d", width, list.Width())
+		}
+
+		removeFn[i]()
+		if list.Width() != width {
+			t.Errorf("Expected width: %d, but got: %d", width, list.Width())
+		}
+	}
+}
+
 func TestFIFOWithWalk(t *testing.T) {
 	list := newRequestFIFO()
 

pkg/util/flowcontrol/fairqueuing/queueset/queueset.go

@@ -438,7 +438,7 @@ func (qs *queueSet) getVirtualTimeRatioLocked() float64 {
 // returns nil in the case that there is no available concurrency or
 // the queuelengthlimit has been reached
 func (qs *queueSet) timeoutOldRequestsAndRejectOrEnqueueLocked(ctx context.Context, width *fqrequest.Width, hashValue uint64, flowDistinguisher, fsName string, descr1, descr2 interface{}, queueNoteFn fq.QueueNoteFn) *request {
-	//	Start with the shuffle sharding, to pick a queue.
+	// Start with the shuffle sharding, to pick a queue.
 	queueIdx := qs.chooseQueueIndexLocked(hashValue, descr1, descr2)
 	queue := qs.queues[queueIdx]
 	// The next step is the logic to reject requests that have been waiting too long
@@ -472,16 +472,18 @@ func (qs *queueSet) timeoutOldRequestsAndRejectOrEnqueueLocked(ctx context.Conte
 // using the given hashValue and the shuffle sharding parameters of the queueSet.
 func (qs *queueSet) chooseQueueIndexLocked(hashValue uint64, descr1, descr2 interface{}) int {
 	bestQueueIdx := -1
-	bestQueueLen := int(math.MaxInt32)
+	bestQueueWidth := int(math.MaxInt32)
 	// the dealer uses the current desired number of queues, which is no larger than the number in `qs.queues`.
 	qs.dealer.Deal(hashValue, func(queueIdx int) {
-		thisLen := qs.queues[queueIdx].requests.Length()
-		klog.V(7).Infof("QS(%s): For request %#+v %#+v considering queue %d of length %d", qs.qCfg.Name, descr1, descr2, queueIdx, thisLen)
-		if thisLen < bestQueueLen {
-			bestQueueIdx, bestQueueLen = queueIdx, thisLen
+		// TODO: Consider taking into account `additional latency` of requests
+		// in addition to their widths.
+		thisWidth := qs.queues[queueIdx].requests.Width()
+		klog.V(7).Infof("QS(%s): For request %#+v %#+v considering queue %d of width %d", qs.qCfg.Name, descr1, descr2, queueIdx, thisWidth)
+		if thisWidth < bestQueueWidth {
+			bestQueueIdx, bestQueueWidth = queueIdx, thisWidth
 		}
 	})
-	klog.V(6).Infof("QS(%s) at r=%s v=%.9fs: For request %#+v %#+v chose queue %d, had %d waiting & %d executing", qs.qCfg.Name, qs.clock.Now().Format(nsTimeFmt), qs.virtualTime, descr1, descr2, bestQueueIdx, bestQueueLen, qs.queues[bestQueueIdx].requestsExecuting)
+	klog.V(6).Infof("QS(%s) at r=%s v=%.9fs: For request %#+v %#+v chose queue %d, had %d waiting & %d executing", qs.qCfg.Name, qs.clock.Now().Format(nsTimeFmt), qs.virtualTime, descr1, descr2, bestQueueIdx, bestQueueWidth, qs.queues[bestQueueIdx].requestsExecuting)
 	return bestQueueIdx
 }
 
@@ -531,7 +533,7 @@ func (qs *queueSet) removeTimedOutRequestsFromQueueLocked(queue *queue, fsName s
 // Otherwise enqueues and returns true.
 func (qs *queueSet) rejectOrEnqueueLocked(request *request) bool {
 	queue := request.queue
-	curQueueLength := queue.requests.Length()
+	curQueueLength := queue.requests.Width()
 	// rejects the newly arrived request if resource criteria not met
 	if qs.totSeatsInUse >= qs.dCfg.ConcurrencyLimit &&
 		curQueueLength >= qs.qCfg.QueueLengthLimit {