General performance issue depending on start method

HI,

i got a very extrange behavior of kodi ( tested with xbmc either ).

when started from command line it works nice 50% – 60% cpu usage tops. Started via startx and .xinitrc.

But when started via rc.local with “su -c /usr/bin/startx kodi” (tried “su -l -c /usr/bin/startx kodi” either ) cpu usuage keeps 90% -100%

Never seen this happend before.

My system is debian/jessie (systemd)

thank you.