On 03/21/2010 02:13 AM, Sebastian Hetze wrote:
> Hi *,
>
> in an 6 CPU SMP guest running on an host with 2 quad core
> Intel Xeon E5520 with hyperthrading enabled
> we see one or more guest CPUs working in a very strange
> pattern. It looks like all or nothing. We can easily identify
> the effected CPU with xosview. Here is the mpstat output
> compared to one regular working CPU:
>
>
> mpstat -P 4 1
> Linux 2.6.31-16-generic-pae (guest) 	21.03.2010 	_i686_	(6 CPU)
> 00:45:19     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest   %idle
> 00:45:20       4    0,00  100,00    0,00    0,00    0,00    0,00    0,00    0,00    0,00
> 00:45:21       4    0,00  100,00    0,00    0,00    0,00    0,00    0,00    0,00    0,00
> 00:45:22       4    0,00  100,00    0,00    0,00    0,00    0,00    0,00    0,00    0,00
> 00:45:23       4    0,00  100,00    0,00    0,00    0,00    0,00    0,00    0,00    0,00
> 00:45:24       4    0,00   66,67    0,00    0,00    0,00   33,33    0,00    0,00    0,00
> 00:45:25       4    0,00  100,00    0,00    0,00    0,00    0,00    0,00    0,00    0,00
> 00:45:26       4    0,00  100,00    0,00    0,00    0,00    0,00    0,00    0,00    0,00
>    

Looks like the guest is only receiving 3-4 timer interrupts per second, 
so time becomes quantized.

Please run the attached irqtop in the affected guest and report the results.

Is the host overly busy?  What host kernel, kvm, and qemu are you 
running?  Is the guest running an I/O workload? if so, how are the disks 
configured?

-- 
error compiling committee.c: too many arguments to function