RE: [Patch] Optimize dropping of relation buffers using dlist

On Thursday, October 1, 2020 4:52 PM, Tsunakawa-san wrote:

> From: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
> > I thought that the advantage of this optimization is that we don't
> > need to visit all buffers? If we need to run a full-scan for any
> > reason, there's no point in looking-up already-visited buffers again.
> > That's just wastefull cycles. Am I missing somethig?
> >
> > I don't understand. If we chose to the optimized dropping, the reason
> > is the number of buffer lookup is fewer than a certain threashold. Why
> > do you think that the fork kind a buffer belongs to is relevant to the
> > criteria?
>
> I rethought about this, and you certainly have a point, but... OK, I think I
> understood. I should have thought in a complicated way. In other words,
> you're suggesting "Let's simply treat all forks as one relation to determine
> whether to optimize," right? That is, the code simple becomes:
>
> Sums up the number of buffers to invalidate in all forks; if (the cached sizes
> of all forks are valid && # of buffers to invalidate < THRESHOLD) {
> do the optimized way;
> return;
> }
> do the traditional way;
>
> This will be simple, and I'm +1.

This is actually close to the v18 I posted trying Horiguchi-san's approach, but that
patch had bug. So attached is an updated version (v20) trying this approach again.
I hope it's bug-free this time.

Regards,
Kirk Jamison