Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock

The more I look at TransactionGroupUpdateXidStatus, the more I think
it's broken, and while we do have some tests, I don't have confidence
that they cover all possible cases.

Or, at least, if this code is good, then it hasn't been sufficiently
explained.

If we have multiple processes trying to write bits to clog, and they are
using different banks, then the LWLockConditionalAcquire will be able to
acquire the bank lock 

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"The saddest aspect of life right now is that science gathers knowledge faster
 than society gathers wisdom."  (Isaac Asimov)