Thanks for the info Paolo and Andi! On Thu, 2020-06-25 at 20:41 +0200, Paolo Bonzini wrote: > On 25/06/20 16:26, Kevin Locke wrote: >> 1. Do I understand correctly that the CPU usage is due to counting >> RTC periodic timer ticks for replay when the guest is resumed? > > Yes. > >> 2. If so, would it be possible to calculate the number of ticks >> required from the time delta at resume, rather than polling each >> tick while paused? > > Note that high CPU usage while the guest is paused is a bug. Only high > CPU usage as soon as the guest resumes is the unavoidable part. [...] >> 5. I have not observed high CPU usage for paused VMs in VirtualBox. >> Would it be worth investigating how they handle this? >> >> From the discussion in https://bugs.launchpad.net/bugs/1851062 it >> appears that the issue does not occur for all Windows 10 VMs. Does >> that fit the theory it is caused by RTC periodic timer ticks? > > Windows 10 can use the Hyper-V synthetic timer instead of the RTC, which > shouldn't have the problem. That's great news! Since I'm able to reproduce the issue on a recently installed Windows 10 2004 VM on Linux 5.7 with QEMU 5.0, is there anything I can do to help isolate the bug, or is it a known issue? Thanks again, Kevin
