DNS caches that support partitioning ?

Are there DNS caches that allow you to partition the cache for subtrees of DNS names? That is, you can say that all entries from say, in-addr.arpa, are limited to 20% of the cache. The application I have in mind is to see if it helps to keep DNSBL traffic, which caches poorly, from pushing other stuff out of the cache, but there are doubtless others. R's, John