10.8.3 seems to be using a lot more swap memory, always increasing (every time mariabackup runs daily)

I don't remember having this issue with 10.5, as although it was using a good amount of swap memory, I never had to do an emergency database restart because of it.

Since a few days ago, I had been receiving alerts about too much swap being used on the server, and it's been getting worse. I had to restart MariaDB yesterday, because it was getting full.

Before the restart, this was the usage:

Resident RAM:
mariadbd – 89387556 (85.25 GB)

Swap:
mariadbd – 26975616 (25.73 GB)

And by the way, my server's sysctl has this config:

vm.swappiness=1
(which means to only use Swap if absolutely necessary; while =0 would disable it)

My innodb_buffer_pool_size is 80G.

Are you aware of any reason so much Swap would be used by MariaDB?

There was plenty of resident free RAM that could be used instead.
I understand that some Swap can be used, but I don't understand why so much Swap, instead of resident RAM.

Since the restart yesterday, it's already using 2GB swap, and increasing.

Thank you.