weird /proc/stat output with newer (4.1, 4.2) kernels in kvm guest on 3.10 host?

[Chris Friesen]

Hi,

I'm running a 3.10-based host with libvirt 1.2.12 and qemu 2.2.

Running a Fedora23 cloud image as a guest, the "cpu" lines in /proc/stat seem to 
be hardly changing:

[fedora@fedora23 boot]$ uptime
 17:01:50 up 44 min,  1 user,  load average: 3.00, 2.99, 2.79
[fedora@fedora23 boot]$ grep cpu /proc/stat
cpu  13 0 124 65880 165 0 0 23088 0 0
cpu0 1 0 4 21967 67 0 0 21866 0 0
cpu1 8 0 52 21877 66 0 0 623 0 0
cpu2 4 0 67 22034 30 0 0 598 0 0


Running an Ubuntu 15.10 cloud image as a guest, everything looks fine:

ubuntu@ubuntu1510:/boot$ uptime
 17:02:28 up 28 min,  1 user,  load average: 3.00, 2.98, 2.42
ubuntu@ubuntu1510:/boot$ grep cpu /proc/stat
cpu  3932 130 443061 46116 257 0 5 12974 0 0
cpu0 1296 130 139886 14960 195 0 1 12343 0 0
cpu1 1330 0 151580 15570 35 0 0 315 0 0
cpu2 1305 0 151595 15586 26 0 4 316 0 0


In both cases the current_clocksource is kvm-clock.  Not sure if it's relevent, 
but Fedora has "CONFIG_NO_HZ_FULL=y" and "CONFIG_NO_HZ_FULL_ALL is not set", and 
does not specify "nohz_full=" in the boot parameters.  Ubuntu has 
"CONFIG_NO_HZ_FULL is not set".


Anyone have any ideas what might be going on?

Chris