pbytes

The initial code cloned from https://github.com/gobwas/pool

Problem

https://research.swtch.com/interfaces

If you try to assign a []byte to an interface{}, the compiler will generate additional conversion code runtime.convTslice and cause memory allocation.

func main() {
	buffer := make([]byte, 0, 64)
	var o interface{} = buffer // CALL    runtime.convTslice(SB)
	fmt.Println(o)
}

convTslice source code https://go.dev/src/runtime/iface.go

func convTslice(val []byte) (x unsafe.Pointer) {
	// Note: this must work for any element type, not just byte.
	if (*slice)(unsafe.Pointer(&val)).array == nil {
		x = unsafe.Pointer(&zeroVal[0])
	} else {
		x = mallocgc(unsafe.Sizeof(val), sliceType, true)
		*(*[]byte)(x) = val
	}
	return
}

(*sync.Pool).Put source code https://go.dev/src/sync/pool.go

// Put adds x to the pool
func (p *Pool) Put(x any) {
    ...
}

var buf = make([]byte, 0, 16)
// equals:
// var x interface{} = buf // CALL    runtime.convTslice(SB)
// pool.Put(x)
pool.Put(buf) 

Resolved

Don't put the []byte into sync.Pool, to resolve the problems, put *[]byte instead.