On Tue, Jun 19, 2012 at 3:48 PM, Andres Freund <and...@2ndquadrant.com> wrote: > Why is that code not used more widely? Quite a bit of our list usage should be > replaced embedding list element in larger structs imo. There are also open- > coded inline list manipulations around (check aset.c for example).
Because we've got a million+ lines of code and nobody knows where all the bodies are buried. > 1. dllist.h has double the element overhead by having an inline value pointer > (which is not needed when embedding) and a pointer to the list (which I have a > hard time seing as being useful) > 2. only double linked list, mine provided single and double linked ones > 3. missing macros to use when embedded in a larger struct (containerof() > wrappers and for(...) support basically) > 4. most things are external function calls... > 5. way much more branches/complexity in most of the functions. My > implementation doesn't use any branches for the typical easy modifications > (push, pop, remove element somewhere) and only one for the typical tests > (empty, has-next, ...) > > The performance and memory aspects were crucial for the aforementioned toy > project (slab allocator for postgres). Its not that crucial for the applycache > where the lists currently are mostly used although its also relatively > performance sensitive and obviously does a lot of list manipulation/iteration. > > If I had to decide I would add the missing api in dllist.h to my > implementation and then remove it. Its barely used - and only in an embedded > fashion - as far as I can see. > I can understand though if that argument is met with doubt by others ;). If > thats the way it has to go I would add some more convenience support for > embedding data to dllist.h and settle for that. I think it might be simpler to leave the name as Dllist and just overhaul the implementation along the lines you suggest, rather than replacing it with something completely different. Mostly, I don't want to add a third thing if we can avoid it, given that Dllist as it exists today is used only lightly. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
