[PATCH 3/6] Add hash support in cache mngr

[Thomas Graf]

On 11/05/12 at 04:43pm, Roopa Prabhu wrote:
> We think route and neigh caches in some cases might grow to that size.
> The patch sets a smaller value to something like a link cache.
> It can be flipped too. Smaller common default size and something
> like route cache gets a larger default value.
> 
> But agreed, I would rather make this user configurable. Which i did
> try to do first time around. But this value should
> be specified at cache allocation time since hash table is allocated
> then. I did not find a clean way to do that. Its possible if we add
> a new cache alloc api or add a new api to add hashtable to an
> existing cache immediately after cache alloc.
> 
> Let me know if you have any preferences.
> 
> Any suggestions on the default hash size ?.

Let's keep the default at 1024 but make the default configurable
by the application:

	nl_config_set_default_htable_size(size_t nelems);

This keeps the default sane for existing users of which some
rely on small memory footprints such as Android while giving
routing daemons or applications a like the chance to user
larger hashtables by default.

We can also allow to resize the hashtable of existing caches. All
objects are on a list so just resize the table and repopulate it
by walking through the list. It's an expensive operation but that
shouldn't matter, we can mark it as such.