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

[Marko ÄukiÄ <marko.djukic@xxxxxxxxx>]

On 13 December 2015 at 12:47, Marko ÄukiÄ <marko.djukic@xxxxxxxxx> wrote:
> Unixbench in a Xen VM is better than on the physical machine.
>
> With flags set to 4147:
> -better by 3.5% for 1 copy of tests
> -better by 3% for 4 parallel copies of tests
>
> With flags set to 4131:
> -better by 4.3% for 1 copy of tests
> -better by 3.8% for 4 parallel copies of tests
>
> I can understand similar results in dhrystone and whetstone because of
> direct execution.
> But I lack the knowledge to understand why Xen is better at tests with
> system calls?
>
> Is it because of VT-x? Can Xen execute system calls "faster" using hardware
> support for virtualization than a physical system using "normal" x86
> and x86_64 calls?
>
> Can someone provide an explanation?
>
> Regards,
>
> Marko


One more question: I am guessing that the value in
/proc/sys/kernel/sched_domain/cpu$f/domain0/flags
is transformed to integer in little endian way, i.e. 4147 equals 0x7414?

Regards,

Marko

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