Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> (As also discussed in the Royal Oak) I think we should simply not dirty
> a page when a hint bit is updated. Reading a page from disk is
> expensive, setting hint bits on the access is generally cheap compared
> to that. But that is orthogonal to the idea of a per-page XID epoch.
I'm not sure it's cheap. What you suggest would result in a substantial
increase in clog accesses, which means (1) more I/O and (2) more
contention. Certainly it's worth experimenting with, but it's no
guaranteed win.
regards, tom lane