kustomize preallocate memory

What this PR does / why we need it:

Preallocate memory instead of enforcing an incremental growth. This will result in less work for the garbage collector.

Oct 06 '22 03:10 florianl

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Oct 06 '22 03:10 k8s-ci-robot

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:white_check_mark: login: florianl / name: Florian Lehner (0fbaa2d0e8d400f5f3a297e6e62667053b0220ca, c2312c4018fe03bb6331846de5d1336938993f44)

Oct 06 '22 03:10 linux-foundation-easycla[bot]

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Oct 06 '22 03:10 k8s-ci-robot

Hi @florianl. Thanks for your PR.

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Oct 06 '22 03:10 k8s-ci-robot

friendly ping at @mengqiy and @mortent - do you have feedback for me on this PR?

Oct 12 '22 16:10 florianl

If this results in a performance improvement, could you please provide some example test cases that demonstrate the optimization? You can refer to https://github.com/kubernetes-sigs/kustomize/pull/4810 as an example, the PR description does a good job of explaining the optimization.

Oct 14 '22 17:10 natasha41575

hi @natasha41575

I'm not sure if it is worth including a benchmark in this PR. But to showcase the performance improvement, I did use the following code:

func BenchmarkStringList(b *testing.B) {
	s := make(String)
	// Prepare s
	for i := 0; i < 1000; i++ {
		s.Insert(fmt.Sprintf("%d", i))
	}
	// Run the benchmark
	for i := 0; i < b.N; i++ {
		list := s.List()
		_ = list
	}
}

On my machine the results for BenchmarkStringList() on this branch are:

$ go test -bench=. -benchmem
goos: linux
goarch: amd64
pkg: sigs.k8s.io/kustomize/kyaml/sets
cpu: AMD Ryzen 7 PRO 4750U with Radeon Graphics
BenchmarkStringList-16    	   34600	     35118 ns/op	   16389 B/op	       1 allocs/op
PASS
ok  	sigs.k8s.io/kustomize/kyaml/sets	1.574s

To compare it with the results from master:

$ go test -bench=. -benchmem
goos: linux
goarch: amd64
pkg: sigs.k8s.io/kustomize/kyaml/sets
cpu: AMD Ryzen 7 PRO 4750U with Radeon Graphics
BenchmarkStringList-16    	   24054	     54318 ns/op	   50423 B/op	      12 allocs/op
PASS
ok  	sigs.k8s.io/kustomize/kyaml/sets	1.816s

So this trivial change reduces the ns/op (from 54318 to 35118) and allocs/op (from 12 to 1).

Oct 18 '22 12:10 florianl

Thanks! /ok-to-test

Oct 18 '22 15:10 natasha41575

/lgtm /approve

Oct 21 '22 21:10 natasha41575

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: florianl, natasha41575

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Oct 21 '22 21:10 k8s-ci-robot