High CPU usage by dwm.exe when nothing is happening
Setup: Windows 7 Ultimate, running in a VMware box inside Windows 8, VMware Tools installed; VMware Workstation is the only application launched in win8). Aero is on.
Starting a few months ago, on and off, performance is extremely sluggish in all applications. Checking process explorer shows high CPU usage by dwm.exe (20-30%) and svchost.exe (30-40%) when system is idle, nothing open but Explorer.
Killing dwm.exe does not change anything; dwm resumes its high cpu usage when it restarts.
Services in svchost are:
- Audio Endpoint Builder
- CSC Service
- Netman
- PCASVC
- SYSMAIN
- TRKWKS
- UXSMS
- WDI System Host
Turning off Aero helps slightly, but I want to actually solve the problem. This problem didn't exist before; it wasn't sluggish, dwm.exe only had high usage when it was actually compositing windows together; I never noticed any high usage from that svchost.
edit when I'm running one app at a time, occasionally large areas of the app go black, like in the olden days with Win 95 when it would run out of system resources.
I would check the amount of video ram VMWare is allocating the the Guest OS. I don't know where the exact configuration options would be inside of VMWare as I don't currently have access to an instance, but I would recommend running dxdiag.exe from within Win7 run prompt and looking to see how much memory the primary display adapter is registering. If this number is low (between 1-128MB), you probably need to allocate more video memory to the guest OS.
DWM is the desktop windows manager which will tend to use resources from the video card. Like an OS installed directly to hardware, if win7 finds that video resources are lacking, it will try to pick up the slack by using CPU resources to compensate.
It also couldn't hurt to either reinstall VMWare tools, or check if there is a newer version available. Since 'Tools probably has components that contribute to the virtualization of video resources, this may be similar to updating your video card driver.