Hedger Lai created YUNIKORN-3463:
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Summary: [Core] Premature loop abort and missing satisfaction
early-stop in calculateAdditionalVictims
Key: YUNIKORN-3463
URL: https://issues.apache.org/jira/browse/YUNIKORN-3463
Project: Apache YuniKorn
Issue Type: Bug
Components: core - scheduler
Reporter: Hedger Lai
Assignee: Hedger Lai
Fix For: 1.6.0
h3. Symptom
In {{Preemptor.calculateAdditionalVictims()}}, preemption for queue quota
exhibits two loop control defects:
1. If an early candidate victim cannot fit in the ask queue's remaining
guaranteed headroom, the loop executes a raw {{break}}, prematurely aborting
the search and starving subsequent viable victims.
2. Conversely, when accumulated victims have already satisfied the ask queue's
guaranteed quota, the loop fails to exit early, scanning remaining victims
unnecessarily.
h3. Root Cause
In {{pkg/scheduler/objects/preemption.go}}:
{code:go}
askQueueRemaining := askQueue.GetRemainingGuaranteedResource()
if askQueueRemaining != nil &&
askQueueRemaining.FitInActual(victim.GetAllocatedResource()) {
askQueue.AddAllocation(victim.GetAllocatedResource())
} else {
queueSnapshot.AddAllocation(victim.GetAllocatedResource())
break // <-- Flaw 1: premature abort on fit failure
}
// ...
// Flaw 2: missing early-stop when quota is already satisfied
{code}
h3. Proposed Fix
1. In the {{else}} branch of {{FitInActual()}}, replace {{break}} with
{{continue}} to evaluate subsequent viable candidates.
2. After appending a valid victim, {{break}} immediately if
{{isAskQueueUnderGuaranteed()}} is satisfied.
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