[jira] [Updated] (YUNIKORN-3463) [Core] Premature loop abort in calculateAdditionalVictims starves preemption

["Hedger Lai (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/YUNIKORN-3463?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hedger Lai updated YUNIKORN-3463:
---------------------------------
    Summary: [Core] Premature loop abort in calculateAdditionalVictims starves preemption  (was: [Core] Premature loop abort and missing satisfaction early-stop in calculateAdditionalVictims)

> [Core] Premature loop abort in calculateAdditionalVictims starves preemption
> ----------------------------------------------------------------------------
>
>                 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
>            Priority: Major
>             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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