may be this would be help:
Syslog: daemon.log
May 1 20:46:31 zwj-desktop rtkit-daemon[1343]: Supervising 1 threads of 1
processes of 1 users.
May 1 20:46:31 zwj-desktop rtkit-daemon[1343]: Sucessfully made thread 32184
of process 32184 (n/a) owned by '1000' high priority at nice leve
I have the problem too. polkitd using 25% cpu and 20% mem.
I suspect
With Debug info:DEBUG: Dropping all .pkla caches for directory
`/etc/polkit-1/localauthority/50-local.d
It seems that it rescan /etc/polkit-1/localauthority over and over again.
The system call is so frequently, that the outp