Re: Improving connection scalability (src/backend/storage/ipc/procarray.c)

Hi,

On 2022-05-24 12:28:20 -0300, Ranier Vilela wrote:
> Linux Ubuntu 64 bits (gcc 9.4)
> ./pgbench -M prepared -c $conns -j $conns -S -n -U postgres
>
> conns tps head tps patched
> 1 2918.004085 3190.810466
> 10 12262.415696 17199.862401
> 50 13656.724571 18278.194114
> 80 14338.202348 17955.336101
> 90 16597.510373 18269.660184
> 100 17706.775793 18349.650150
> 200 16877.067441 17881.250615
> 300 16942.260775 17181.441752
> 400 16794.514911 17124.533892
> 500 16598.502151 17181.244953
> 600 16717.935001 16961.130742
> 700 16651.204834 16959.172005
> 800 16467.546583 16834.591719
> 900 16588.241149 16693.902459
> 1000 16564.985265 16936.952195

17-18k tps is pretty low for pgbench -S. For a shared_buffers resident run, I
can get 40k in a single connection in an optimized build. If you're testing a
workload >> shared_buffers, GetSnapshotData() isn't the bottleneck. And
testing an assert build isn't a meaningful exercise either, unless you have
way way higher gains (i.e. stuff like turning O(n^2) into O(n)).

What pgbench scale is this and are you using an optimized build?

Greetings,

Andres Freund