Re: shared-memory based stats collector

At Tue, 07 Apr 2020 16:38:17 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
> At Fri, 03 Apr 2020 17:31:17 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
> > Conflicted with the commit 28cac71bd3 - SLRU stats.
> >
> > Rebased and fixed some issues.
> > - A PoC (or a rush work) of refactoring of SLRU stats.
> >
> > I tried to combine it into the global stats hash, but the SLRU
> > report functions are called within critical sections so memory
> > allocation fails. The current pgstat module removes the local entry
> > at successful flushing out to shared stats, so allocation at the
> > first report is inevitable. In the attched version it is handled
> > the same way with global stats. I continue seeking a way to
> > combining it to the global stats hash.
>
> I didn't find a way to consolidate into the general local stats
> hash. The hash size could be large and the chance of allocation
> failure is larger than other places where in-critical-section memory
> allocation is allowed. Instead, in the attached, I separated
> shared-SLRU lock from StatsLock and add the logic to avoid useless
> scan on the array.

Maybe 29c3e2dd5a and recent doc change hit this. Rebased.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center