Interesting CPU Usage reverse problem, but Why?

Interesting CPU Usage reverse problem, but Why?

[Peijie Yu]

Hi

I have met an interesting problem between different kvm&linux version.
Both the two run on the same platform.

HW Platform:
Processors | physical = 2, cores = 8, virtual = 16, hyperthreading = yes

Speeds | 16x2266.804
Models | 16xIntel(R) Xeon(R) CPU E5520 @ 2.27GHz
Caches | 16x8192 KB
Memory | 23.54G
OS        | CentOS 5



Configuration 1:
     Configuration:2
Kernel | 2.6.18-194.el5
 Kernel | 2.6.32-71.24.1.el6.x86_64
Architecture | CPU = 64-bit, OS = 64-bit
KVM  | kvm-83-164.el5_5.23                                         KVM
    | Follow kernel's version

Guest:
Configuration 1:
                   Configuration:2
Platform | Windows
 Release | Windows Server 2003 Enterprise Edition SP2
Processors | SMP=4
             Processor | SMP=2
Memory | 4G



I run the wprime in the Guest;  From Guest's Task Manager, the CPU Usage is 100%
In both Configurations, the corresponding PCPU is 100% too from Linux
Host's top view.

And in Configuration 1, the PCPU's cpu time is nearly 100% in sys space.
But in Configuration 2, the situation is totally reversed, the PCPU's
time is nearly 100% in Usr space.



Could anyone tell me the reason?

Thank you very much!

Best Regards

Peijie Yu

Re: Interesting CPU Usage reverse problem, but Why?

[Avi Kivity]

On 05/27/2011 11:44 AM, Peijie Yu wrote:
> Hi
>
> I have met an interesting problem between different kvm&linux version.
> Both the two run on the same platform.
>
> HW Platform:
> Processors | physical = 2, cores = 8, virtual = 16, hyperthreading = yes
>
> Speeds | 16x2266.804
> Models | 16xIntel(R) Xeon(R) CPU E5520 @ 2.27GHz
> Caches | 16x8192 KB
> Memory | 23.54G
> OS        | CentOS 5
>
>
>
> Configuration 1:
>       Configuration:2
> Kernel | 2.6.18-194.el5
>   Kernel | 2.6.32-71.24.1.el6.x86_64
> Architecture | CPU = 64-bit, OS = 64-bit
> KVM  | kvm-83-164.el5_5.23                                         KVM
>      | Follow kernel's version
>
> Guest:
> Configuration 1:
>                     Configuration:2
> Platform | Windows
>   Release | Windows Server 2003 Enterprise Edition SP2
> Processors | SMP=4
>               Processor | SMP=2
> Memory | 4G
>
>
>
> I run the wprime in the Guest;  From Guest's Task Manager, the CPU Usage is 100%
> In both Configurations, the corresponding PCPU is 100% too from Linux
> Host's top view.
>
> And in Configuration 1, the PCPU's cpu time is nearly 100% in sys space.
> But in Configuration 2, the situation is totally reversed, the PCPU's
> time is nearly 100% in Usr space.
>
>
>
> Could anyone tell me the reason?
>

Modern kernels account guest time as user time (since it wasn't spent in 
the host kernel).

-- 
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