I agree with Tom's reasoning about the suggested simplifications, sorry.

> > 3. Should the WALWriter also do the wal_buffers half-full write at
> > start of XLogInsert() ?
> That should go away entirely; to me the main point of the 
> separate wal-writer process is to take over responsibility 
> for not letting too many dirty wal buffers accumulate.

That also sounds a lot simpler, but I think Bruce wanted to be able to
some time guarantee to the not waiting for fsync txns.
When a commit only half-filled the page and no more WAL comes in for 
a long time, there is only WALWriter to do the IO.
The WALWriter would need to only flush a half-full page after timeout
iff it contains a commit record.

One more question on autocommit:
Do we wait for a flush for an autocommitted DML ?
Seems we generally should not.


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