Re: Configurable FP_LOCK_SLOTS_PER_BACKEND

>
> Why would the access frequency be uniform? In particular, there's a huge
> variability in how long the locks need to exist
>

As a supporting data point, our example production workload shows a 3x
difference between the most versus least frequently contended lock_manager
lock:
https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/2301#note_1365630726

Since we deterministically distribute relations among those 16 lock_manager
lwlocks by hashing their lock tag, we can probably assume a roughly uniform
number of relations are being managed by each lock_manager lock, but the
demand (and contention) for them is non-uniform. This 3x spread
corroborates the intuition that some relations are locked more frequently
than others (that being both a schema- and workload-specific property).

Since we're contemplating a new hashing scheme, I wonder how we could
accommodate that kind of asymmetry, where some relations are locked more
frequently than others.