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Merge pull request #78009 from hainesc/develop

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Use reservoir sampling to select one host from priority list
This commit is contained in:
Kubernetes Prow Robot 2019-08-01 00:52:15 -07:00 committed by GitHub
commit ac1cde5577
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1 changed files with 19 additions and 24 deletions
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43
pkg/scheduler/core/generic_scheduler.go
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@ -20,6 +20,7 @@ import (
"context" "context"
"fmt" "fmt"
"math" "math"
"math/rand"
"sort" "sort"
"strings" "strings"
"sync" "sync"
@ -160,7 +161,6 @@ type genericScheduler struct {
prioritizers []priorities.PriorityConfig prioritizers []priorities.PriorityConfig
framework framework.Framework framework framework.Framework
extenders []algorithm.SchedulerExtender extenders []algorithm.SchedulerExtender
lastNodeIndex uint64
alwaysCheckAllPredicates bool alwaysCheckAllPredicates bool
nodeInfoSnapshot *internalcache.NodeInfoSnapshot nodeInfoSnapshot *internalcache.NodeInfoSnapshot
volumeBinder *volumebinder.VolumeBinder volumeBinder *volumebinder.VolumeBinder
@ -271,34 +271,29 @@ func (g *genericScheduler) Predicates() map[string]predicates.FitPredicate {
return g.predicates return g.predicates
} }
// findMaxScores returns the indexes of nodes in the "priorityList" that has the highest "Score".
func findMaxScores(priorityList schedulerapi.HostPriorityList) []int {
maxScoreIndexes := make([]int, 0, len(priorityList)/2)
maxScore := priorityList[0].Score
for i, hp := range priorityList {
if hp.Score > maxScore {
maxScore = hp.Score
maxScoreIndexes = maxScoreIndexes[:0]
maxScoreIndexes = append(maxScoreIndexes, i)
} else if hp.Score == maxScore {
maxScoreIndexes = append(maxScoreIndexes, i)
}
}
return maxScoreIndexes
}
// selectHost takes a prioritized list of nodes and then picks one // selectHost takes a prioritized list of nodes and then picks one
// in a round-robin manner from the nodes that had the highest score. // in a reservoir sampling manner from the nodes that had the highest score.
func (g *genericScheduler) selectHost(priorityList schedulerapi.HostPriorityList) (string, error) { func (g *genericScheduler) selectHost(priorityList schedulerapi.HostPriorityList) (string, error) {
if len(priorityList) == 0 { if len(priorityList) == 0 {
return "", fmt.Errorf("empty priorityList") return "", fmt.Errorf("empty priorityList")
} }
maxScore := priorityList[0].Score
maxScores := findMaxScores(priorityList) selected := priorityList[0].Host
ix := int(g.lastNodeIndex % uint64(len(maxScores))) cntOfMaxScore := 1
g.lastNodeIndex++ for _, hp := range priorityList[1:] {
if hp.Score > maxScore {
return priorityList[maxScores[ix]].Host, nil maxScore = hp.Score
selected = hp.Host
cntOfMaxScore = 1
} else if hp.Score == maxScore {
cntOfMaxScore++
if rand.Intn(cntOfMaxScore) == 0 {
// Replace the candidate with probability of 1/cntOfMaxScore
selected = hp.Host
}
}
}
return selected, nil
} }
// preempt finds nodes with pods that can be preempted to make room for "pod" to // preempt finds nodes with pods that can be preempted to make room for "pod" to