Dear hackers,
> As per the above observations, it is less of a regression of this
> feature but more of a lack of parallel apply or some kind of pre-fetch
> for apply, as is recently proposed [1]. I feel there are use cases, as
> explained above, for which this feature would work without any
> downside, but due to a lack of some sort of parallel apply, we may not
> be able to use it without any downside for cases where the contention
> is only on a smaller set of tables. We have not tried, but may in
> cases where contention is on a smaller set of tables, if users
> distribute workload among different pub-sub pairs by using row
> filters, there also, we may also see less regression. We can try that
> as well.
I verified row filter idea by benchmark and this was the valid approach.
Please see the below report.
Highlights
=======
- No regression was observed when publisher changes were processed by multiple
apply workers on the subscriber.
Used source
=========
pgHead commit 62a17a92833 + v47 patch set
Machine details
===========
Intel(R) Xeon(R) CPU E7-4890 v2 @ 2.80GHz CPU(s) :88 cores, - 503 GiB RAM
Setup
====
- Publisher and Subscriber nodes are created with configurations:
autovacuum = false
shared_buffers = '30GB'
-- Also, worker and logical replication related parameters were increased
as needed (see attached scripts for details).
Workload
======
- The publisher has 4 pgbench tables: pgbench_pub_accounts, pgbench_pub_tellers,
pgbench_pub_branches, and pgbench_pub_history
- Also the publisher has 15 publications, say pub_[0..14]. Each publications could
publish tuples which PK % 15 was same as their suffic
- Ran pgbench with 15 clients for the *both side*.
- On subscriber, there were 15 subscribers which subscribed one of the publication
- On subscriber, the default pgbench workload is also run.
- The duration was 5 minutes, and the measurement was repeated 3 times.
Test Scenarios & Results:
Publisher:
- pgHead : Median TPS = 12201.92205
- pgHead + patch : Median TPS = 12368.58001
(TPS reduced ~1.5%)
Subscriber:
- pgHead : Median TPS = 11264.78483
- pgHead + patch : Median TPS = 11471.8107
(TPS reduced ~1.8%)
Observation:
- No performance regression was observed on either the publisher or subscriber
with the patch applied.
Detailed Results Table
======================
Publisher:
#run head patched
1 12201.92205 12368.58001
2 12263.03531 12410.21465
3 12171.24214 12330.47522
median 12201.92205 12368.58001
Subscriber:
#run head patched
1 11383.51717 11471.8107
2 11264.78483 11422.47011
3 11146.6676 11518.8403
median 11264.78483 11471.8107
Best regards,
Hayato Kuroda
FUJITSU LIMITED
