[Xen-devel] Fwd: Benchmark in the VM

[suixiufeng <suixiufeng@xxxxxxxxx>]

---------- Forwarded message ----------
From: suixiufeng <suixiufeng@xxxxxxxxx>
Date: 2012/5/22
Subject: Re: [Xen-devel] Benchmark in the VM
To: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>

The dom0 kernel is centos5.5, and the Hypervisor is xen-4.1.2. The domU kernel is centos5.5, which is installed through the virt-install command (I think it belongs to HVM).

Then I use xenoprof to collect the cycle, instruction number, LLC access number and LLC miss number information when running spec cpu 2006 benchmarks.

And I found the instruction number increased significantly as shown in my last email.

I don't know what's the reason.

2012/5/22 George Dunlap <George.Dunlap@xxxxxxxxxxxxx>

On Tue, May 22, 2012 at 7:51 AM, suixiufeng <suixiufeng@xxxxxxxxx> wrote:
> Hi,
>    When I run some workloads from SPECCPU2006. I found that the retired
> instruction number vary significantly between VM and PM according to
> xenoprof. For example:
>
>    Workload                                            Insts
>                            Platform
>    435.gromacs (CPU intensive)                4458151
>                 PM
>    435.gromacs                                       151265683
>                     VM
>    450.soplex   (Memory intensive)            760142
>                PM
>     450.soplex                                          23311208
>                        VM
>
> What is the reason? Does Xen use interpret? Thank you!

I take you to mean, "Does Xen emulate guest instructions"?  The answer
is "No", with one exception: for HVM guests, Xen will emulate accesses
to devices, including MMIO and PIO.

There's not really enough information here to even make a guess as to
what might be causing your numbers here; it's not even really clear
what the numbers you're reporting are, as they seem to be instructions
rather than the performance.  If you could give a bit more information
about what kind of guest OS you're running, your setup, how you're
collecting data, and what it means, we might be able to be more
helpful.

 -George

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