Fix preemption algorithm to reduce the number of preemptions

[mimowo]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #1974

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Fix preemption algorithm to reduce the number of preemptions within a ClusterQueue when reclamation is not possible.

[mimowo]

/cc @alculquicondor

[netlify]

✅ Deploy Preview for kubernetes-sigs-kueue canceled.

Name	Link
🔨 Latest commit	7ca5892
🔍 Latest deploy log	https://app.netlify.com/sites/kubernetes-sigs-kueue/deploys/661d3a429236bb0008c1e581

[alculquicondor]

Are we still reaching this branch with any of the test cases? In particular, for reclaimWithinCohort: Any.

[alculquicondor]

I'm tempted to remove it.

[mimowo]

Yes, we have a failing unit test in preemption_test.go: "preempting locally and borrowing other resources in cohort, without cohort candidates" (yes it is using reclaimWithinCohort: LowerPriority, but I checked that it also fails if we change reclaimWithinCohort to Any.

I would suggest keeping it (at least in this PR, and probably its removal would require a feature gate).

However, your comment prompted me to think of a cleaner code structure, so that return minimalPreemptions(wlReq, cq, assignment, snapshot, resPerFlv, sameQueueCandidates, true, nil) appears only once in code. PTAL.

[alculquicondor]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 3056eeffb692abb2029f27bed48374df8e635da4

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alculquicondor, mimowo

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• pkg/OWNERS [alculquicondor,mimowo]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[alculquicondor]

/release-note-edit

Fix preemption algorithm to reduce the number of preemptions within a ClusterQueue when reclamation is not possible.

[k8s-ci-robot]

@alculquicondor: /release-note-edit must be used with a release note block.

In response to this:

/release-note-edit

Fix preemption algorithm to reduce the number of preemptions within a ClusterQueue when reclamation is not possible.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[alculquicondor]

/release-note-edit

Fix preemption algorithm to reduce the number of preemptions within a ClusterQueue when reclamation is not possible.

[alculquicondor]

/cherry-pick release-0.6

[k8s-infra-cherrypick-robot]

@alculquicondor: once the present PR merges, I will cherry-pick it on top of release-0.6 in a new PR and assign it to you.

In response to this:

/cherry-pick release-0.6

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-infra-cherrypick-robot]

@alculquicondor: #1979 failed to apply on top of branch "release-0.6":

Applying: Fix preemption algorithm to reduce the number of preemptions
Using index info to reconstruct a base tree...
M	pkg/scheduler/preemption/preemption.go
M	pkg/scheduler/scheduler_test.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/scheduler/scheduler_test.go
CONFLICT (content): Merge conflict in pkg/scheduler/scheduler_test.go
Auto-merging pkg/scheduler/preemption/preemption.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Fix preemption algorithm to reduce the number of preemptions
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-0.6

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.