Messages in this thread | | | Date | Thu, 3 Mar 2016 12:36:02 -0600 | From | Chris Friesen <> | Subject | Re: weird /proc/stat output with newer (4.1, 4.2) kernels in kvm guest on 3.10 host? |
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On 03/02/2016 11:12 AM, Chris Friesen wrote: > 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.
Quick update (sorry it's not threaded, I'm not subscribed to the list).
The problem seems to be related to VIRT_CPU_ACCOUNTING being enabled in the guest. If I switch to TICK_CPU_ACCOUNTING or IRQ_TIME_ACCOUNTING then the problem goes away.
I'm digging into the code now. Anyone have any tips on debugging why VIRT_CPU_ACCOUNTING is misbehaving in the guest?
Thanks, Chris
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