Re: [patch][rfc] ddds: "dynamic dynamic data structure" algorithm, for adaptive dcache hash table sizing (resend)

Nick Piggin
2008-10-07T16:39:39Z

On Wednesday 08 October 2008 02:37, Mikael Pettersson wrote:

> I missed the first post, but loooking at the patch it seems
> somewhat complex.

It is complex, but relatively self-contained, ie. it doesn't affect
the actual code that performs hash lookups very much (although there
can be some impact on atomicity if we have to consider something like
a full table traversal like the rt hash).

> How does this relate to traditional incremental hash tables
> like extensible hashing or linear hashing (not to be confused
> with linear probing)? In linear hashing a resize only affects
> a single collision chain at a time, and reads from other chains
> than the one being resized are unaffected.

I haven't actually seen any real implementations of those things.
AFAICS they don't exactly deal with concurrency. They are also likely
to be more costly to operate on, versus a well sized simple hash
table.