If I run Linux kernel 22.214.171.124 and then start a qemu virtual machine running
Windows XP as the guest operating system the CPU usage is high, always close to
100%, and the virtual machine slower than normal.
Once I am able to log in to windows, task manager shows the CPU usage
permanently at 100%, even when Windows should be idle, and higher than normal
usage from the csrss process. I attach a screen shot of task manager showing
this. Looking at the CPU usage from Linux when windows is idle it is notable
that most of the CPU usage is user-mode.
By comparison, with exactly the same virtual hard disk image and the same
version of qemu (and kqemu) and kernel 126.96.36.199 the CPU usage is much lower
and windows runs faster. When windows is idle the CPU usage is low and when
Windows is active the CPU usage is approximately 2/3 user and 1/3 system.
The qemu versions concerned are as follows:
The hardware is an AMD64 processor and 1GB RAM.
The problem with 2.6.24 seems only to occur with kqemu and also appears in
dependant of whether dynamic ticks is enabled. A couple of timings should
illustrate the difference.
>From VM start to login prompt: no kqemu=2m0s, 2.6.23=1m2s, 2.6.24=1m27s.
>From login to last systray icon: no kqemu=6m25s, 2.6.23=1m47s, 2.6.24=4m46s
Does anyone have any insight as to what may be happening or what tools I could
use to gather enough information to help you guys diagnose the problem?