Re: [Xen-users] Xen VMs and Unixbench: single vs multiple cpu behaviour

[Sarah Newman <srn@xxxxxxxxx>]

On 11/14/2015 11:03 PM, Marko ÄukiÄ wrote:
> Hello!
> I am doing a comparison of different hypervisors using the Unixbench 
> benchmark software. 
> The testing is done on a machine with an Intel Core i5 cpu (4 cores).
> 
> I am running two series of tests: 
> - test A: 10 repetitions of the unixbench test in a VM with 1 cpu
> - test B: 10 repetitions of the same test in a VM with 4 cpus
> 
> Test B has two sets of results because in a multicpu machine Unixbench runs a
>  single test first (let's call it B-1) and then runs 4 tests in parallel - 
> one for each cpu (test B-2).
> 
> Compared to other hypervisors, in Xen VMs the results of tests A and B-2 are 
> very good.
> Results of B-1, however, are much worse at tests with system calls.
> For example:
> 
> Xen VM:
> test A create process test average score: 1871,7
> test B-1 create process test average score: 286,7 (!)
> test B-2 create process test average score:3259,2
> Qemu/KVM VM:
> test A create process test average score: 1865,6
> test B-1 create process test average score: 1095,3
> test B-2 create process test average score:3271,7
> 
> Comparing total unixbench score Xen outperforms Qemu/KVM in tests A and B-2.
> 
> Can anybody explain such a large difference in performance in test B-1 in Xen 
> compared to Qemu/KVM? 

I can guess, but to confirm is it 32 or 64 bit and what type of guest are you 
using? See
http://wiki.xen.org/wiki/Xen_Project_Software_Overview#Guest_Types

Slide 36 of 
http://events.linuxfoundation.org/sites/events/files/slides/pvh-linux-collab-summit_0.pdf
 (March 2014) compares PV, HVM, and PVH.

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