toKill := len(old) - toKeep
	if toKill <= 0 {
		return nil
	}

	// Find all hashes of live pods
	liveHashes := make(map[string]bool)
	for _, pods := range nodesToDaemonPods {
		for _, pod := range pods {
			if hash := pod.Labels[apps.DefaultDaemonSetUniqueLabelKey]; len(hash) > 0 {
				liveHashes[hash] = true
			}
		}
	}

	// Clean up old history from smallest to highest revision (from oldest to newest)