Table partitioning takes too long on 16 cores server

I’m trying to create a new partition (LIST) on an existing table (innodb) with 30copy to tmp table" state.
I have used the percona mysql performance wizard to improve and I don’t see any differences. The server is with no traffic at all.
Running on Ubuntu server with 16cores, 30GB memory and SSD 300/3000 IO. it looks like the mysql is not using all resources. the memory usage is on 9GB and only 3 cores are running on very low load.
Is there a way to improve setting to use more resources and speed up the query?

Thanks