[dpdk-dev] [PATCH 0/3] add new Double Word Key hash table

[Stephen Hemminger]

On Mon, 16 Mar 2020 18:27:40 +0000
"Medvedkin, Vladimir" <vladimir.medvedkin at intel.com> wrote:

> Hi Morten,
> 
> 
> On 16/03/2020 14:39, Morten Brørup wrote:
> >> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Vladimir Medvedkin
> >> Sent: Monday, March 16, 2020 2:38 PM
> >>
> >> Currently DPDK has a special implementation of a hash table for
> >> 4 byte keys which is called FBK hash. Unfortunately its main drawback
> >> is that it only supports 2 byte values.
> >> The new implementation called DWK (double word key) hash
> >> supports 8 byte values, which is enough to store a pointer.
> >>
> >> It would also be nice to get feedback on whether to leave the old FBK
> >> and new DWK implementations, or whether to deprecate the old one?  
> > <rant on>
> >
> > Who comes up with these names?!?
> >
> > FBK (Four Byte Key) and DWK (Double Word Key) is supposed to mean the same. Could you use 32 somewhere in the name instead, like in int32_t, instead of using a growing list of creative synonyms for the same thing? Pretty please, with a cherry on top!  
> 
> 
> That's true, at first I named it as fbk2, but then it was decided to 
> rename it "dwk", so that there was no confusion with the existing FBK 
> library. Naming suggestions are welcome!
> 
> >
> > And if the value size is fixed too, perhaps the name should also indicate the value size.
> >
> > <rant off>
> >
> > It's a shame we don't have C++ class templates available in DPDK...
> >
> > In other news, Mellanox has sent an RFC for an "indexed memory pool" library [1] to conserve memory by using uintXX_t instead of pointers, so perhaps a variant of a 32 bit key hash library with 32 bit values (in addition to 16 bit values in FBK and 64 bit in DWK) would be nice combination with that library.
> >
> > [1]: http://mails.dpdk.org/archives/dev/2019-October/147513.html
> >
> >
> > Med venlig hilsen / kind regards
> > - Morten Brørup
> >  

Why is this different (or better) than existing rte_hash.
Having more flavors is not necessarily a good thing (except in Gelato)