Since doing a fresh install of Windows 8 Pro RTM x64 English on my Sony Vaio Z21 laptop, I've been bothered by a sudden increase in fan noise whenever I leave the machine idle for a while and the displays are turned off. Finally decided to try and get to the bottom of it today, so I ran the Performance Recorder with the CPU usage profile enabled and brought up the relevant graphs in Performance Analyzer. See the below screen shot for the results.
I started the trace and then left the machine alone for a while to trigger the idle behavior. It's pretty clear that Dwm.exe is the main culprit. As to why this process would find anything useful to do when all the displays are turned off is beyond me. Also Outlook.exe sees a significant increase of CPU usage during the same time period. Whether these two are somehow related, I have no clue. Please note that I've disabled all other processes in the graph for clarity; no other processes showed any visible increase during the trace.
Any advice would be greatly appreciated!
Daniel Stolt, Perceptible, http://www.perceptible.net