size   int // max size
	npages int // number of pages
}

func powerOfTwo(x int) bool {
	return x != 0 && x&(x-1) == 0
}

func makeClasses() []class {
	var classes []class

	classes = append(classes, class{}) // class #0 is a dummy entry

	align := minHeapAlign
	for size := align; size <= maxSmallSize; size += align {
		if powerOfTwo(size) { // bump alignment once in a while
			if size >= 2048 {