12c background processes

Hi All,

I have a question around 12c shared background processes for container database. Assuming If i have a CDB and 50 PDB's and most of these pdb's are busy in transactions how does these single set of background processes like DBWR,LGWR,SMON,PMON etc will operate on these PDB's parallely ? will the background processes create a slave processes for each PDB? Wont there be any performance issue as the background processes are shared for all PDB's?

Thanks

Hemanth