X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/498d29adee40f671fd2924c410226db7a6a0ba93..355173ba2e8c42b29011493d1d8c7cc4d69295c6:/services/crunch-dispatch-slurm/priority.go

diff --git a/services/crunch-dispatch-slurm/priority.go b/services/crunch-dispatch-slurm/priority.go
index 8c27043051..2312ce5952 100644
--- a/services/crunch-dispatch-slurm/priority.go
+++ b/services/crunch-dispatch-slurm/priority.go
@@ -4,19 +4,27 @@
 
 package main
 
+const defaultSpread int64 = 10
+
 // wantNice calculates appropriate nice values for a set of SLURM
 // jobs. The returned slice will have len(jobs) elements.
 //
-// spread is a non-negative amount of space to leave between adjacent
+// spread is a positive amount of space to leave between adjacent
 // priorities when making adjustments. Generally, increasing spread
 // reduces the total number of adjustments made. A smaller spread
 // produces lower nice values, which is useful for old SLURM versions
 // with a limited "nice" range and for sites where SLURM is also
 // running non-Arvados jobs with low nice values.
+//
+// If spread<1, a sensible default (10) is used.
 func wantNice(jobs []*slurmJob, spread int64) []int64 {
 	if len(jobs) == 0 {
 		return nil
 	}
+
+	if spread < 1 {
+		spread = defaultSpread
+	}
 	renice := make([]int64, len(jobs))
 
 	// highest usable priority (without going out of order)
@@ -27,13 +35,13 @@ func wantNice(jobs []*slurmJob, spread int64) []int64 {
 			// priority container gets the highest
 			// possible slurm priority.
 			target = job.priority + job.nice
-		} else if space := target - job.priority; space >= 0 && space < spread*10 {
+		} else if space := target - job.priority; space >= 0 && space < (spread-1)*10 {
 			// Ordering is correct, and interval isn't too
 			// large. Leave existing nice value alone.
 			renice[i] = job.nice
 			target = job.priority
 		} else {
-			target -= spread
+			target -= (spread - 1)
 			if possible := job.priority + job.nice; target > possible {
 				// renice[i] is already 0, that's the
 				// best we can do