Re: Tracking disk writes? (again)

Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Tom Lane wrote:
>> One of the reasons you don't see that is that a large fraction of the
>> writes are triggered in background by the "bgwriter" process, which
>> operates at too low a level to participate in the stats collection
>> mechanism. I'm not sure what would be involved in refactoring things
>> sufficiently to make that workable, but it'd be nontrivial.

> You mean that bgwriter cannot send stat messages?

Right. The stats mechanism is attached to relcache entries, which the
bgwriter doesn't have. And if it did collect stats, it would never send
them because that happens in the outer postgres.c loop (it's not totally
clear what would be a good granularity for sending them in bgwriter).
And I think it is not a backend in the stats collector's eyes, either.

Surely these things could be dealt with, but it'd take some refactoring.

regards, tom lane