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

Hi, Andres and Alexander!

On Tue, 7 Mar 2023, 10:10 Alexander Korotkov, <aekorotkov(at)gmail(dot)com> wrote:

> On Tue, Mar 7, 2023 at 4:50 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2023-03-02 14:28:56 +0400, Pavel Borisov wrote:
> > > 2. Heap updates with low tuple concurrency:
> > > Prepare with pkeys (pgbench -d postgres -i -I dtGvp -s 300
> --unlogged-tables)
> > > Update 3*10^7 rows, 50 conns (pgbench postgres -f
> > > ./update-only-account.sql -s 300 -P10 -M prepared -T 600 -j 5 -c 50)
> > >
> > > Result: Both patches and master are the same within a tolerance of
> > > less than 0.7%.
> >
> > What exactly does that mean? I would definitely not want to accept a 0.7%
> > regression of the uncontended case to benefit the contended case here...
>
> I don't know what exactly Pavel meant, but average overall numbers for
> low concurrency are.
> master: 420401 (stddev of average 233)
> patchset v11: 420111 (stddev of average 199)
> The difference is less than 0.1% and that is very safely within the error.
>

Yes, the only thing that I meant is that for low-concurrency case the
results between patch and master are within the difference between repeated
series of measurements. So I concluded that the test can not prove any
difference between patch and master.

I haven't meant or written there is some performance degradation.

Alexander, I suppose did an extra step and calculated overall average and
stddev, from raw data provided. Thanks!

Regards,
Pavel.

>