I have Linux Mint 17.3 with Multi-Core System Monitor and the same issue with polkitd process.
I have noticed that removing the Multi-Core applet from the panel and adding it again, causes polkitd to increase the cpu usage. It started with 4%, after one restart to 8%, then another restart to 12% and then 16%.
I have disabled the applet and restarted the system. Now polkitd is at 0% of CPU usage and 7.2Mb of RAM since half hour.
I have Linux Mint 17.3 with Multi-Core System Monitor and the same issue with polkitd process.
I have noticed that removing the Multi-Core applet from the panel and adding it again, causes polkitd to increase the cpu usage. It started with 4%, after one restart to 8%, then another restart to 12% and then 16%.
I have disabled the applet and restarted the system. Now polkitd is at 0% of CPU usage and 7.2Mb of RAM since half hour.