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