Re: New statistics for tuning WAL buffer size

On Tue, Sep 29, 2020 at 7:39 AM Masahiro Ikeda <ikedamsh(at)oss(dot)nttdata(dot)com> wrote:
>
> On 2020-09-28 12:43, Amit Kapila wrote:
> > On Mon, Sep 28, 2020 at 8:24 AM Kyotaro Horiguchi
> > <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> >>
> >> At Mon, 28 Sep 2020 08:11:23 +0530, Amit Kapila
> >> <amit(dot)kapila16(at)gmail(dot)com> wrote in
> >> > One other thing that occurred to me today is can't we keep this as
> >> > part of PgStat_GlobalStats? We can use pg_stat_reset_shared('wal'); to
> >> > reset it. It seems to me this is a cluster-wide stats and somewhat
> >> > similar to some of the other stats we maintain there.
> >>
> >> I like that direction, but PgStat_GlobalStats is actually
> >> PgStat_BgWriterStats and cleard by a RESET_BGWRITER message.
> >>
> >
> > Yeah, I think if we want to pursue this direction then we probably
> > need to have a separate message to set/reset WAL-related stuff. I
> > guess we probably need to have a separate reset timestamp for WAL. I
> > think the difference would be that we can have one structure to refer
> > to global_stats instead of referring to multiple structures and we
> > don't need to issue separate read/write calls but OTOH I don't see
> > many disadvantages of the current approach as well.
>
> IIUC, if we keep wal stats as part of PgStat_GlobalStats,
> don't we need to add PgStat_ArchiverStats and PgStat_SLRUStats
> to PgStat_GlobalStats too?
>

I have given the idea for wal_stats because there is just one counter
in that. I think you can just try to evaluate the merits of each
approach and choose whichever you feel is good. This is just a
suggestion, if you don't like it feel free to proceed with the current
approach.

--
With Regards,
Amit Kapila.