Checking the Xorg server code, the following procedures make the RRGetInfo call, which seems to lead to the expensive probe:
ProcRRGetScreenSizeRange ProcRRGetScreenResources ProcRRGetScreenInfo ProcRRSetScreenConfig
Checking the Xorg server code, the following procedures make the RRGetInfo call, which seems to lead to the expensive probe:
ProcRRGetScreen SizeRange Resources Config
ProcRRGetScreen
ProcRRGetScreenInfo
ProcRRSetScreen