Re: Discordant results between UnixBench and nBench

[Avi Kivity <avi@redhat.com>]

On 12/23/2009 11:43 AM, Matthieu Olivier wrote:
> All,
>
> I am performing a study about KVM.
> (Shame on me, I did not check the version of kvm module. All I know is
> that I was using the last Red Hat EL 5.4. Anyway).
>
>   I used a DELL server 2950, with:
> - 1 processor Xeon L5240 (3 Ghz, 6 Mo cache)
> - 8 GB of RAM
> - 4 disks SAS 15k in RAID-1
>
> I created a procedure consist to launch a benchmark on several
> virtual machine at the same time. Each session consist in testing X VM,
> where X comes from 1 to 8. With nbench, I collected all results and
> extracted an average value of results for each VM. Then, I multiplied
> these average values by the number of VM in test, getting one unique
> and generic value per session of test.
> I did nearly the same with unixbench.
>
> On the host side, I launched the same tests, except that instead of
> running them in separate VM, I just launched several threads at the
> same time thanks to a script.
>
> My main purpose is watching the overhead due to these different
> hypervisors, according bechmark results. I am not really in trouble
> with KVM itself, but results of my benchmarks:
>
> ->  http://img121.imageshack.us/img121/9279/nbench.png
> ->  http://img704.imageshack.us/img704/953/unixbench.png
>
> Indeed, where I have all results growing from 1 VM tested to 8 VM, we
> can see the host growing from 1 to 8 VM. which seems good. But KVM
> only increases from 1 to 4 VM, and then stays on the same order of
> results, without growing anymore.
> The situation is inverse on Unixbench, where KVM seems to
> follow host's performances.
>    

What does 'top' show for nbench with 8 guests?  How about kvm_stat?

Are the results different for the 8 guests, or are they all making the 
same progress?

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