Re: Wait free LW_SHARED acquisition - v0.2

Some background:
The setups that triggered me into working on the patchset didn't really
have a pgbench like workload, the individual queries were/are more
complicated even though it's still an high throughput OLTP workload. And
the contention was *much* higher than what I can reproduce with pgbench
-S, there was often nearly all time spent in the lwlock's spinlock, and
it was primarily the buffer mapping lwlocks, being locked in shared
mode. The difference is that instead of locking very few buffers per
query like pgbench does, they touched much more.