Scheduler first fit

[aleksandra-malinowska]

Resubmit of #122058, reverted in #122317 due to a flaky test

Test is fixed now - there was a typo, node3 instead of node2 was listed as one of expected results.

What type of PR is this?

/kind bug

What this PR does / why we need it:

Skip looking for extra nodes if no scoring plugins are defined. As there's no difference in priority between nodes when we don't score them, there's no point in searching for multiple fitting nodes.

Which issue(s) this PR fixes:

Fixes #122057

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Improves scheduler performance when no scoring plugins are defined.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

/sig scheduling
/cc @ahg-g

[k8s-ci-robot]

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[aleksandra-malinowska]

Flakes should be gone now:

~/go/src/k8s.io/kubernetes/pkg/scheduler$ go test -count 100 -run TestSchedulerSchedulePod
PASS
ok      k8s.io/kubernetes/pkg/scheduler 274.489s

[ahg-g]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: dfc829cf71cd090cfd82a8d8f582343fe1fe8fc0

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, aleksandra-malinowska

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• pkg/scheduler/OWNERS [ahg-g]

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[pacoxu]

~/go/src/k8s.io/kubernetes/pkg/scheduler$ go test -count 100 -run TestSchedulerSchedulePod
PASS
ok k8s.io/kubernetes/pkg/scheduler 274.489s

Have you tried stress to reproduce the flake? stress can reproduce the flake in high load and multi times runnings.
See https://gist.github.com/liggitt/6a3a2217fa5f846b52519acfc0ffece0#running-unit-tests-to-reproduce-flakes for more details.

This adding test https://prow.k8s.io/view/gs/kubernetes-jenkins/logs/ci-kubernetes-unit/1740254928200273920 flakes in master blocking test grid.

I opened #122505 to track the new flake.

Read more in https://github.com/kubernetes/community/blob/master/contributors/devel/sig-testing/flaky-tests.md.

[aleksandra-malinowska]

This was reverted in #123290