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

On Wed, January 13, 2021 2:15 PM (JST), Amit Kapila wrote:
> On Wed, Jan 13, 2021 at 7:39 AM Kyotaro Horiguchi
> <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> >
> > At Tue, 12 Jan 2021 08:49:53 +0530, Amit Kapila
> > <amit(dot)kapila16(at)gmail(dot)com> wrote in
> > > On Fri, Jan 8, 2021 at 7:03 AM Kyotaro Horiguchi
> > > <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> > > >
> > > > At Thu, 7 Jan 2021 09:25:22 +0000, "k(dot)jamison(at)fujitsu(dot)com"
> <k(dot)jamison(at)fujitsu(dot)com> wrote in:
> > > > > > Thanks for the detailed tests. NBuffers/32 seems like an
> > > > > > appropriate value for the threshold based on these results. I
> > > > > > would like to slightly modify part of the commit message in
> > > > > > the first patch as below [1], otherwise, I am fine with the
> > > > > > changes. Unless you or anyone else has any more comments, I am
> > > > > > planning to push the 0001 and 0002 sometime next week.
> > > > > >
> > > > > > [1]
> > > > > > "The recovery path of DropRelFileNodeBuffers() is optimized so
> > > > > > that scanning of the whole buffer pool can be avoided when the
> > > > > > number of blocks to be truncated in a relation is below a
> > > > > > certain threshold. For such cases, we find the buffers by doing
> lookups in BufMapping table.
> > > > > > This improves the performance by more than 100 times in many
> > > > > > cases when several small tables (tested with 1000 relations)
> > > > > > are truncated and where the server is configured with a large
> > > > > > value of shared buffers (greater than 100GB)."
> > > > >
> > > > > Thank you for taking a look at the results of the tests. And
> > > > > it's also consistent with the results from Tang too.
> > > > > The commit message LGTM.
> > > >
> > > > +1.
> > > >
> > >
> > > I have pushed the 0001.
> >
> > Thank you for commiting this.
> >
>
> Pushed 0002 as well.
>

Thank you very much for committing those two patches, and for everyone here
who contributed in the simplifying the approaches, code reviews, testing, etc.

I compile with the --enable-coverage and check if the newly-added code and updated
parts were covered by tests.
Yes, the lines were hit including the updated lines of DropRelFileNodeBuffers(),
DropRelFileNodesAllBuffers(), smgrdounlinkall(), smgrnblocks().
Newly added APIs were covered too: FindAndDropRelFileNodeBuffers() and
smgrnblocks_cached().
However, the parts where UnlockBufHdr(bufHdr, buf_state); is called is not hit.
But I noticed that exists as well in previously existing functions in bufmgr.c.

Thank you very much again.

Regards,
Kirk Jamison