Stabilize: map declaration syntax

[jordalgo]

This unstable feature was added here: #3863

This is an umbrella issue to track fixes/features required to stabilize this feature (e.g. remove the need for the unstable_map_decl config flag).

[jordalgo]

Current feature requests:

• Add BPF_MAP_TYPE_TASK_STORAGE (Issue) - This requires a bit more plumbing but we should do it. The declaration might look like let @a = taskstorage() where no or 0 max entries is allowed.

[jordalgo]

• Allow interleaving of macros and map decls #4242

[ajor]

Can we change the names of the map types prior to stabilisation? :)

hash -> hash_map etc.

hash makes it sound like we're just storing a hashed value, rather than a key-value pair. "Hash map" is a more commonly understood term for this kind of data structure: https://en.wikipedia.org/wiki/Hash_table

If we support BPF_MAP_TYPE_ARRAY in the future then that could be just array though - as it's not a "map" in the standard data structure sense.

[jordalgo]

@ajor Do you think that means we should add the _map suffix to all the hash map types:

• percpulruhash
• percpuhash
• lruhash

percpulruhashmap or per_cpu_lru_hash_map feel a bit long

[ajor]

Hmmm good point...

Neither "LRU Hash" nor "LRU Hash Map" are really standard terms either - that data structure would be more commonly known as an LRU Cache (e.g. https://www.boost.org/doc/libs/1_67_0/boost/compute/detail/lru_cache.hpp). There seems to be some precedent for shortening this to just "LRU" though: https://docs.rs/lru/latest/lru/ https://github.com/hashicorp/golang-lru

What do you think?

[jordalgo]

We could just have multiple names for each one. There wouldn't be lexer pollution and they also wouldn't conflict with macros or UDFs since they are assignments at the top level.

• hash and hash_map
• lruhash and lru
• percpulruhash and percpulru