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

Hi!

On Sun, Mar 12, 2023 at 7:05 PM Alexander Korotkov <aekorotkov@gmail.com> wrote:
> The revised patch set is attached.  Some comments are improved.  Also,
> we implicitly skip the new facility for the MERGE case.  As I get Dean
> Rasheed is going to revise the locking for MERGE soon [1].
>
> Pavel, could you please re-run your test case on the revised patch?

I found the experiments made by Pavel [1] hard to reproduce due to the
high variation of the TPS.  Instead, I constructed a different
benchmark, which includes multiple updates (40 rows) in one query, and
run it on c5d.18xlarge.  That produces stable performance results as
well as measurable performance benefits of the patch.

I found that patchsets v11 and v14 not showing any performance
improvements over v10.  v10 is also much less invasive for
heap-related code.  This is why I made v15 using the v10 approach and
porting  LazyTupleTableSlot and improved comments there.  I think this
should address some of Andres's complaints regarding introducing too
much infrastructure [2].

The average results for high concurrency case (errors are given for a
95% confidence level) are given below.  We can see that v15 gives a
measurable performance improvement.

master = 40084 +- 447 tps
patchset v10 = 41761 +- 1117 tps
patchset v11 = 41473 +- 773 tps
patchset v14 = 40966 +- 1008 tps
patchset v15 = 42855 +- 977 tps

The average results for low concurrency case (errors are given for a
95% confidence level) are given below. It verifies that the patch
introduces no overhead in the low concurrency case.

master = 50626 +- 784 tps
patchset v15 = 51297 +- 876 tps

See attachments for raw experiment data and scripts.

So, as we can see patch gives a small performance improvement for the
heap in edge high concurrency case.  But also it improves table AM API
for future use cases [3][4].

I'm going to push patchset v15 if no objections.

Links
1. https://www.postgresql.org/message-id/CALT9ZEHKdCF_jCoK2ErUuUtCuYPf82%2BZr1XE5URzneSFxz3zqA%40mail.gmail.com
2. https://www.postgresql.org/message-id/20230308012157.wo73y22ll2cojpvk%40awork3.anarazel.de
3. https://www.postgresql.org/message-id/CAPpHfdu1dqqcTz9V9iG-ZRewYAFL2VhizwfiN5SW%3DZ%2B1rj99-g%40mail.gmail.com
4. https://www.postgresql.org/message-id/167846860062.628976.2440696515718158538.pgcf%40coridan.postgresql.org

------
Regards,
Alexander Korotkov