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

[Marko ÄukiÄ <marko.djukic@xxxxxxxxx>]

Hello!

I am doing a comparison of different hypervisors using the Unixbench benchmark software.Â

The testing is done on a machine with an Intel Core i5 cpu (4 cores).

I am running two series of tests:Â

- 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

Âsingle 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 XenÂ

compared to Qemu/KVM?Â

I noticed the same behaviour using Xen 4.4.2 and 4.5.1 (both installed with default

options in ubuntu server 14.04.2 and 15.10 respectively).

Regards

Marko

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