[Codel] [Bloat] found another good use for a queue today, possibly

Jonathan Morton chromatix99 at gmail.com
Mon Nov 26 23:17:19 EST 2018

>> "polylog(n)-wise Independent Hash Function". OK, my google-foo fails
>> me: The authors use sha1, would something lighter weight suit?

> The current favorite in DPDK land seems to be Cuckoo hashing.
> It has better cache behavior than typical chaining.

That paper describes an improved variant of cuckoo hashing, using a queue to help resolve collisions with better time complexity.  The proof relies on (among other things) a particular grade of hash function being used.  SHA1 is described as being suitable since it offers cryptographic-level performance…  We actually need two hashes with independent behaviour on the same input, one for each table.

If we were to assume table sizes up to 64K, using both halves of a good 32-bit hash might be suitable.  It may be that plain old Jenkins hash would work in that context.  Supplement that with a 64-entry queue with linear search (in software) or constant-time CAM search (in hardware).

 - Jonathan Morton

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