pgcat decreases TPS from unproxied posgresql 16 by 4x to 5x (docker-compose reproducer)

[cpbotha]

Describe the bug Performance of pgcat unexpectedly low on x86 hardware, but not on Apple Silicon.

Platform	baseline 10	pgcat 10	pgcat 100
m1max	154	624	577
ryzen 5900x wsl	133	19	19
i7-8750H ubuntu	88	20	20

I hope I'm doing something wrong. :)

To Reproduce docker-compose reproducer: https://github.com/cpbotha/pgcat-docker-compose-demo

From that readme:

Start the cluster:

docker-compose up

Try with pgbench:

# https://www.postgresql.org/docs/current/pgbench.html
# init "postgres" database for pgbench
pgbench -p 6432 -h localhost -i -U postgres postgres
# baseline perf with 10 clients to the bare postgres
pgbench -p 5432 -h localhost -T 20 -C -c 10 -n -U postgres postgres
# 10 clients via pgcat
pgbench -p 6432 -h localhost -T 20 -C -c 10 -n -U postgres postgres
# 100 clients via pgcat
# bench with 100 clients for 20 seconds
# -C: new connection for each transaction
# -n: no vacuuming before running test
pgbench -p 6432 -h localhost -T 20 -C -c 100 -n -U postgres postgres

Expected behavior

Going via pgcat should not decrease TPS by 4x to 5x like it does on x86.

[saolof]

Not a maintainer here, but I'm wondering about whether you pulled the image or if you tried building it locally from the dockerfile? Differences between architecture may be fixable by tweaking the release profile and adding compilation flags or enabling/disabling jemalloc. Also, I assume you ran all the tests in docker? Since afaik docker on mac runs in its own vm.

I have a fairly powerful AMD server at work that we are currently in the middle of doing benchmarking on to evaluate different database configurations, and we are considering benchmarking pgcat as well. Do you see a similar dropoff at all pool sizes or just at 10?

[cpbotha]

it's pulling exactly the same image, please see the linked reproducer project.

what's interesting, is that that exact same config is giving pretty good perf on apple silicon where the x86 is being emulated (!!), with the perf on native x86 being super sad.

I would be really curious to hear about the outcomes of your benchmarks if you do decide to add pgcat to the mix. I did not experiment with different pool sizes yet, probably won't have time soon, have had to postpone the pgcat integration work due to this perf issue.

[levkk]

I suspect the pgcat docker image is out of date since our Github action that publishes it is currently broken. There was a fix for this issue released recently in #749.