I've just added tallying of idle time in the VM so that the system report can give more meaningful overheads to the GC information it reports. Currently the VM tallies idle time in the innards of relinquishProcessorForMicroseconds:. But it also needs to tally idle time across SLEEP/WAKE events. May I ask experts in the Mac OS, X11 and Windows worlds to have a loop at event processing and either implement tallying idle time here or reporting back on what work is required or (as I fear in the case of X11/Unix) whether it is unsupported.
Here's an example of the nonsense one gets back after waking one's laptop: