Lockless pg_buffercache

Hi,

I want to use the pg_buffercache contrib module for monitoring our
server. It takes a lock on all buffers and then on each buffer header
in order to get a consistent picture of the buffers. I would be
running the function provided by the module once every 5 minutes.

I'm worrying about the performance hit of that - a comment in the code
says it's horrible for concurrency. Additionally, as I don't use this
for debugging, but just for monitoring, I don't need a 100% consistent
picture, just rough numbers how much of the buffer cache is used for
what relation.

Does removing all locking as in the attached patch have any negative
impact other than the non-consistency of the results?

Thanks

Markus