X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/d6e1bfee59569d79f0f3e24620280e70aa161403..1d36bef0f6e0a64d4d7660f5db8e9625d99302c6:/services/crunch-dispatch-slurm/squeue.go

diff --git a/services/crunch-dispatch-slurm/squeue.go b/services/crunch-dispatch-slurm/squeue.go
index fd4851eb0a..0ce4fb6732 100644
--- a/services/crunch-dispatch-slurm/squeue.go
+++ b/services/crunch-dispatch-slurm/squeue.go
@@ -33,7 +33,8 @@ type SqueueChecker struct {
 	queue          map[string]*slurmJob
 	startOnce      sync.Once
 	done           chan struct{}
-	sync.Cond
+	lock           sync.RWMutex
+	notify         sync.Cond
 }
 
 // HasUUID checks if a given container UUID is in the slurm queue.
@@ -42,11 +43,11 @@ type SqueueChecker struct {
 func (sqc *SqueueChecker) HasUUID(uuid string) bool {
 	sqc.startOnce.Do(sqc.start)
 
-	sqc.L.Lock()
-	defer sqc.L.Unlock()
+	sqc.lock.RLock()
+	defer sqc.lock.RUnlock()
 
 	// block until next squeue broadcast signaling an update.
-	sqc.Wait()
+	sqc.notify.Wait()
 	_, exists := sqc.queue[uuid]
 	return exists
 }
@@ -55,26 +56,31 @@ func (sqc *SqueueChecker) HasUUID(uuid string) bool {
 // container.
 func (sqc *SqueueChecker) SetPriority(uuid string, want int64) {
 	sqc.startOnce.Do(sqc.start)
-	sqc.L.Lock()
-	defer sqc.L.Unlock()
-	job, ok := sqc.queue[uuid]
-	if !ok {
+
+	sqc.lock.RLock()
+	job := sqc.queue[uuid]
+	if job == nil {
 		// Wait in case the slurm job was just submitted and
 		// will appear in the next squeue update.
-		sqc.Wait()
-		if job, ok = sqc.queue[uuid]; !ok {
-			return
-		}
+		sqc.notify.Wait()
+		job = sqc.queue[uuid]
+	}
+	needUpdate := job != nil && job.wantPriority != want
+	sqc.lock.RUnlock()
+
+	if needUpdate {
+		sqc.lock.Lock()
+		job.wantPriority = want
+		sqc.lock.Unlock()
 	}
-	job.wantPriority = want
 }
 
 // adjust slurm job nice values as needed to ensure slurm priority
 // order matches Arvados priority order.
 func (sqc *SqueueChecker) reniceAll() {
-	sqc.L.Lock()
-	defer sqc.L.Unlock()
-
+	// This is slow (it shells out to scontrol many times) and no
+	// other goroutines update sqc.queue or any of the job fields
+	// we use here, so we don't acquire a lock.
 	jobs := make([]*slurmJob, 0, len(sqc.queue))
 	for _, j := range sqc.queue {
 		if j.wantPriority == 0 {
@@ -82,7 +88,7 @@ func (sqc *SqueueChecker) reniceAll() {
 			// (perhaps it's not an Arvados job)
 			continue
 		}
-		if j.priority == 0 {
+		if j.priority <= 2*slurm15NiceLimit {
 			// SLURM <= 15.x implements "hold" by setting
 			// priority to 0. If we include held jobs
 			// here, we'll end up trying to push other
@@ -133,13 +139,6 @@ func (sqc *SqueueChecker) Stop() {
 // queued). If it succeeds, it updates sqc.queue and wakes up any
 // goroutines that are waiting in HasUUID() or All().
 func (sqc *SqueueChecker) check() {
-	// Mutex between squeue sync and running sbatch or scancel.  This
-	// establishes a sequence so that squeue doesn't run concurrently with
-	// sbatch or scancel; the next update of squeue will occur only after
-	// sbatch or scancel has completed.
-	sqc.L.Lock()
-	defer sqc.L.Unlock()
-
 	cmd := sqc.Slurm.QueueCommand([]string{"--all", "--noheader", "--format=%j %y %Q %T %r"})
 	stdout, stderr := &bytes.Buffer{}, &bytes.Buffer{}
 	cmd.Stdout, cmd.Stderr = stdout, stderr
@@ -160,6 +159,10 @@ func (sqc *SqueueChecker) check() {
 			log.Printf("warning: ignoring unparsed line in squeue output: %q", line)
 			continue
 		}
+
+		// No other goroutines write to jobs' priority or nice
+		// fields, so we can read and write them without
+		// locks.
 		replacing, ok := sqc.queue[uuid]
 		if !ok {
 			replacing = &slurmJob{uuid: uuid}
@@ -191,18 +194,20 @@ func (sqc *SqueueChecker) check() {
 			// resolved the same way.
 			log.Printf("releasing held job %q (priority=%d, state=%q, reason=%q)", uuid, p, state, reason)
 			sqc.Slurm.Release(uuid)
-		} else if p < 1<<20 && replacing.wantPriority > 0 {
+		} else if state != "RUNNING" && p <= 2*slurm15NiceLimit && replacing.wantPriority > 0 {
 			log.Printf("warning: job %q has low priority %d, nice %d, state %q, reason %q", uuid, p, n, state, reason)
 		}
 	}
+	sqc.lock.Lock()
 	sqc.queue = newq
-	sqc.Broadcast()
+	sqc.lock.Unlock()
+	sqc.notify.Broadcast()
 }
 
 // Initialize, and start a goroutine to call check() once per
 // squeue.Period until terminated by calling Stop().
 func (sqc *SqueueChecker) start() {
-	sqc.L = &sync.Mutex{}
+	sqc.notify.L = sqc.lock.RLocker()
 	sqc.done = make(chan struct{})
 	go func() {
 		ticker := time.NewTicker(sqc.Period)
@@ -214,6 +219,15 @@ func (sqc *SqueueChecker) start() {
 			case <-ticker.C:
 				sqc.check()
 				sqc.reniceAll()
+				select {
+				case <-ticker.C:
+					// If this iteration took
+					// longer than sqc.Period,
+					// consume the next tick and
+					// wait. Otherwise we would
+					// starve other goroutines.
+				default:
+				}
 			}
 		}
 	}()
@@ -223,9 +237,9 @@ func (sqc *SqueueChecker) start() {
 // names reported by squeue.
 func (sqc *SqueueChecker) All() []string {
 	sqc.startOnce.Do(sqc.start)
-	sqc.L.Lock()
-	defer sqc.L.Unlock()
-	sqc.Wait()
+	sqc.lock.RLock()
+	defer sqc.lock.RUnlock()
+	sqc.notify.Wait()
 	var uuids []string
 	for u := range sqc.queue {
 		uuids = append(uuids, u)