Improve performance of NodeResourcesFit scoring

[alculquicondor]

What would you like to be added?

Profiling reveals that a non-negligible amount of time is wasted creating and querying small maps (example: make(resourceToValueMap), with an expected size of 2 or 3). I believe we should be able to replace them with slices for a performance boost.

We should build unit-level benchmarks to proof that the improvements are good, similar to

kubernetes/pkg/scheduler/framework/plugins/podtopologyspread/scoring_test.go

Line 1272 in 8f2371b

func BenchmarkTestPodTopologySpreadScore(b *testing.B) {

Why is this needed?

While the plugin has decent performance, if we try to push the limits of kube-scheduler, there's still room for improvement.

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[alculquicondor]

/sig scheduling

[aojea]

I believe we should be able to replace them with slices for a performance boost.

have you considered sync.Pool? https://pkg.go.dev/sync#example-Pool

[alculquicondor]

That sounds like more overhead than a simple slice. These are all sync operations.

[ruquanzhao]

Hi, @alculquicondor
Could I take a shot on this?

If I understand correctly,
we need a func BenchmarkTestFitScore() in fit_test.go, then compare slices and small maps.

[alculquicondor]

yes, that's roughly the plan. There will be a lot of trial-and-error.

[tangwz]

/assign

[ruquanzhao]

/assign

[tangwz]

/assign

@ruquanzhao I've already started. Do you want to continue?

[alculquicondor]

/unassign @Zhaoruquan

This was already assigned.

[alculquicondor]

/unassign @ruquanzhao

[tangwz]

@alculquicondor

If I understand correctly, I need to add a test function like mostResourceScorer and use resourceToValueSlice instead of resourceToValueMap, then add a func BenchmarkTestFitScore() in fit_test.go and run it.

kubernetes/pkg/scheduler/framework/plugins/noderesources/most_allocated.go

Line 29 in 8f2371b

func mostResourceScorer(resToWeightMap resourceToWeightMap) func(requested, allocable resourceToValueMap) int64 {

[alculquicondor]

I suggest you first add the benchmark. Then, try to replace the maps with slices. Probably both resourceToValueMap and resourceToWeightMap. You can use the profiler on the benchmark to see the effects of your changes.

[tangwz]

I suggest you first add the benchmark. Then, try to replace the maps with slices. Probably both resourceToValueMap and resourceToWeightMap. You can use the profiler on the benchmark to see the effects of your changes.

Thanks.