I installed PXC & PS 57 on centos7 and both of them have this in the error log:

This means thread priorities are disabled (for page_cleaner and lru threads) when you install the package. This is at least on every environment. See bug: https://bugs.mysql.com/bug.php?id=85175

During some insert benchmarks I was quickly able to get:

Now to configure the limits, with systemd you cannot do this with /etc/security/limits.conf as is described in https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_page_cleaners. Systemd ignores this file.

You have to apply it with a systemd config file:

note that you have to type systemctl daemon-reload when you want to apply this

Here's how to check the limit of a running daemon:
when not configured:

when configured:

I suggest we add this to the RPM package, for non systemd systems we can maybe use /etc/security/limits.d/*.conf files (if they read it).