Re: [dpdk-dev] DPDK Hash library

[Matthew Hall <mhall@mhcomputing.net>]

On Jul 2, 2015, at 4:20 AM, Dumitrescu, Cristian <cristian.dumitrescu@intel.com> wrote:
> I am wondering how can I use the hash library if I don't know the number
> of entries in the bucket (number of entries in the bucket can grow
> dynamically)
> I am trying to use the DPDK hash library for MAC table where I can't give
> the fixed number of elements in each bucket.

Another thing to keep in mind. DPDK hashes have an extremely large number of shallow buckets and pretty good spreading hash functions, This is for performance reasons to minimize the amount of cacheline loads. The chances of evicting buckets in this sort of hash table aren't really all that high so worrying about this might be overkill.

If you want a good quality hash table for weird stuff like variable-length keys, deeper buckets to guarantee items are preserved, etc., what I ended up doing was combining uthash with jemalloc in my app (you could also use rte_malloc but I didn't want to complicate the app too much until I get it feature complete and begin tuning it).

https://troydhanson.github.io/uthash/
https://github.com/troydhanson/uthash

http://www.canonware.com/jemalloc/
https://github.com/jemalloc/jemalloc

Matthew.