Re: POC: Lock updated tuples in tuple_update() and tuple_delete()

On Thu, Mar 2, 2023 at 9:17 PM Pavel Borisov <pashkin.elfe@gmail.com> wrote:
> On Thu, 2 Mar 2023 at 18:53, Alexander Korotkov <aekorotkov@gmail.com> wrote:
> > On Thu, Mar 2, 2023 at 1:29 PM Pavel Borisov <pashkin.elfe@gmail.com> wrote:
> > > > Let's see the performance results for the patchset.  I'll properly
> > > > revise the comments if results will be good.
> > > >
> > > > Pavel, could you please re-run your tests over revised patchset?
> > >
> > > Since last time I've improved the test to avoid significant series
> > > differences due to AWS storage access variation that is seen in [1].
> > > I.e. each series of tests is run on a tmpfs with newly inited pgbench
> > > tables and vacuum. Also, I've added a test for low-concurrency updates
> > > where the locking optimization isn't expected to improve performance,
> > > just to make sure the patches don't make things worse.
> > >
> > > The tests are as follows:
> > > 1. Heap updates with high tuple concurrency:
> > > Prepare without pkeys (pgbench -d postgres -i -I dtGv -s 10 --unlogged-tables)
> > > Update tellers 100 rows, 50 conns ( pgbench postgres -f
> > > ./update-only-tellers.sql -s 10 -P10 -M prepared -T 600 -j 5 -c 50 )
> > >
> > > Result: Average of 5 series with patches (0001+0002) is around 5%
> > > faster than both master and patch 0001. Still, there are some
> > > fluctuations between different series of the measurements of the same
> > > patch, but much less than in [1]
> >
> > Thank you for running this that fast!
> >
> > So, it appears that 0001 patch has no effect.  So, we probably should
> > consider to drop 0001 patch and consider just 0002 patch.
> >
> > The attached patch v12 contains v11 0002 patch extracted separately.
> > Please, add it to the performance comparison.  Thanks.
>
> I've done a benchmarking on a full series of four variants: master vs
> v11-0001 vs v11-0001+0002 vs v12 in the same configuration as in the
> previous measurement. The results are as follows:
>
> 1. Heap updates with high tuple concurrency:
> Average of 5 series v11-0001+0002 is around 7% faster than the master.
> I need to note that while v11-0001+0002 shows consistent performance
> improvement over the master, its value can not be determined more
> precisely than a couple of percents even with averaging. So I'd
> suppose we may not conclude from the results if a more subtle
> difference between v11-0001+0002 vs v12 (and master vs v11-0001)
> really exists.
>
> 2. Heap updates with high tuple concurrency:
> All patches and master are still the same within a tolerance of
> less than 0.7%.
>
> Overall patch v11-0001+0002 doesn't show performance degradation so I
> don't see why to apply only patch 0002 skipping 0001.

Thank you, Pavel.  So, it seems that we have substantial benefit only
with two patches.  So, I'll continue working on both of them.

------
Regards,
Alexander Korotkov