silbinarywolf / practice-bump-allocator

A bump allocator built in Go

Practice Bump Allocator

⚠️ This library is not supported and should not be used as-is for any purpose

This is my first attempt at building a bump / pool / arena allocator in Go 1.16. There were no real goals in mind at the beginning other than to see if I...

• Could do it
• Make it faster
• Make it as safe as possible while retaining maintainability

Unfortunately in my investigation of building this, I found that unless you accessed reflect data directly and unsafely, you would pay heavy allocation and speed costs and so I put together a small subset of the reflect package so I could do this, with tests that check my implementation against the reflect package to ensure parity. I've found if you don't do something like this, your bump allocator will end up allocating anyway via the reflect package and you gain nothing, but I didn't dive too deep, so I'd be happy to be wrong about this.

Results from testing

$ go test ./... -count=1 -bench=.
goos: windows
goarch: amd64
pkg: github.com/silbinarywolf/practice-bump-allocator
cpu: AMD Ryzen 5 3600 6-Core Processor
BenchmarkNativeAlloc1000-12       613857              1879 ns/op            3200 B/op        100 allocs/op
BenchmarkAlloc1000-12            2159748               555.5 ns/op             0 B/op          0 allocs/op
PASS
ok      github.com/silbinarywolf/practice-bump-allocator        2.997s
PASS
ok      github.com/silbinarywolf/practice-bump-allocator/internal/inlinetest    0.123s
PASS
ok      github.com/silbinarywolf/practice-bump-allocator/internal/reflectlite   0.062s

For readability convenience, relevant code copy-pasted out of bump_test.go

type Player struct {
	X, Y          int
	Width, Height int
}

// BenchmarkNativeAlloc is here so we can compare native Go
// allocations to our bump allocator
func BenchmarkNativeAlloc1000(b *testing.B) {
	b.ReportAllocs()

	var p1 *Player

	for n := 0; n < b.N; n++ {
		for i := 0; i < 100; i++ {
			p1 = &Player{}
		}
	}

	_ = p1
}

func BenchmarkAlloc1000(b *testing.B) {
	b.ReportAllocs()

	var p1 *Player

	alloc := New(make([]byte, 32678))
	for n := 0; n < b.N; n++ {
		for i := 0; i < 100; i++ {
			p1 = alloc.New(&Player{}).(*Player)
		}
		alloc.Reset()
	}

	_ = p1
}