Hello Bhaskar, On Tue, Oct 29, 2013 at 11:56:50PM -0400, Bhaskar Maddala wrote: > Hello Willy, > > In continuation of the thread on alternatives to consistent hashing, I > am starting a new thread to track the patch that has been implemented. > > The results of testing can be viewed at [1]. The result match my > expectations from earlier, i.e. when using consistent hashing DJB2 is > better than the alternatives.
OK then probably we don't need wt6 if it does not bring anything here. We don't need to add features that provide no value and that people will want to use because they decide so! I just noticed that Bob Jenkins has run a comparison of multiple hashes including DJB2 which in his opinion is good for english text : http://www.burtleburtle.net/bob/hash/doobs.html Never tried Spookyhash though, Murmur3 nor siphash though. > I will run the additional test for 1MM > requests and fill in the results shortly, however I was satisfied to send > this patch along. Please lmk in case of any questions. OK. I'm thinking about something we discussed about earlier in this thread, to have the ability to disable avalanche. I think we could do this *and* keep the compatibility with existing configs with what you've done : hash-type {map-based|consistent} [<algo>] <algo> would be "sdbm", "djb2", "wt6", "sdbm+avalanche", "djb2+avalanche", "wt6+avalanche". "consistent" would default to "sdbm+avalanche". The keyword "avalanche" alone would still be accepted for the first keyword as an alias for "map-based sdbm+avalanche" but be deprecated (and probably removed in the 1.5 release). Note that we could also consider not doubling the keywords and proceeding like this instead since "avalanche" is always optional with any hash : hash-type {map-based|consistent} [[<algo>] avalanche] > The attached patch was generated with "git format-patch master > --stdout", here are some stats Don't worry about the stats, you can simply post the output of git format-patch, it's easily understandable. I quickly glanced over the patch because I must leave in a few minutes and my general feeling is that it's OK. Please consider the options above concerning the split of "avalanche" and about still allowing as a separate keyword but deprecated. I think this will open the way to add more hash functions in the future, especially if we want to add some mixing functions (like avalanche) which re-hash 32-bit into 32-bit. Thanks for the great work and all the testing, I know what it means to produce that many values! Willy
