Re: per backend I/O statistics

On Wed, Nov 20, 2024 at 02:20:18PM +0000, Bertrand Drouvot wrote:
> Right. I did not had in mind to go that far here (for the per backend stats
> needs). My idea was "just" to move the new pgstat_create_backend_stat() (which
> is related to per backend stats only) call at the right place in StartupXLOG()
> for the startup process only. As that's the startup process that will reset
> or restore the stats I think that makes sense.
>
> It looks like that what you have in mind is much more generic, what about:
>
> - Focus on this thread first and then move the call as proposed above
> - Think about a more generic idea later on (on the per-backend I/O stats is
> in).

Moving pgstat_create_backend_stat() may be OK in the long-term, at
least that would document why we need to care about the startup
process.

Still, moving only the call feels incomplete, so how about adding a
boolean field in PgStat_ShmemControl that defaults to false when the
shmem area is initialized in StatsShmemInit(), then switched to true
once we know that the stats have been restored or reset by the startup
process. Something like that should work to control the dshash
inserts, I guess?
--
Michael