Re: [dpdk-dev] [PATCH 0/7] Add Membership Library

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 21 Aug 2017 17:19:46 -0700
Yipeng Wang <yipeng1.wang@intel.com> wrote:

> This patch set implements two types of set-summaries, i.e., hash-table based
> set-summary (HTSS) and Vector Bloom Filter (vBF). HTSS supports both the
> non-cache and cache modes. The non-cache mode can incur a small chance of
> false-positives which is the case when the set-summary indicates a key belongs
> to a given set while actually it is not. The cache mode can also have
> false-negatives in addition to false-positives. False-negatives means the case
> when the set-summary indicates a key does not belong to a given set while
> actually it does. This happens because cache mode allows new key to evict
> existing keys. vBF only has false-positives similar to the non-cache HTSS.
> However, one can set the false-positive rate arbitrarily. HTSS's
> false-positive rate is determined by the hash-table size and the signature size.

I don't think it makes sense to merge two different types  of  tables in one
API. Especially in DPDK where every cycle counts. You are taking an extra branch
on each lookup. The user of this API is likely to know exactly what type
of objects and look are desired.