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

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Thu, 2015-11-26 at 18:03 +0100, Marko ÄukiÄ wrote:
> On 26 November 2015 at 09:26, Dario Faggioli <dario.faggioli@xxxxxxxx
> om> wrote:
> > >Â
> Contents of /proc/sys/kernel/sched_domain/cpu0/domain0/name:
> DIE
> Contents of /proc/sys/kernel/sched_domain/cpu0/domain0/flags:
> 4143
> 
Ok, as I was expecting, and as I'm seeing too.

Thanks for doing this.

So, quick and dirty: if you change (by `echo >`-ing) the value of
flags, you'll see performance boost. I'm quite sure that will be the
case for UnixBench, and I'm trying to verify whether that is consistent
with other benchamrks too.

For instance, you can try 4131 or 4147. Remember to do that for all the
vCPUs:

for f in `seq 0 3`;do echo 4131 > 
/proc/sys/kernel/sched_domain/cpu$f/domain0/flags ; done;

Basically, what you are doing, is altering the Linux's load balancing
behavior, in a way that it interacts better with Xen's scheduler.

The various flags are defined here:
http://lxr.free-electrons.com/source/include/linux/sched.h#L978

I'll follow up with a more detailed explanation, and with more numbers,
as soon as practical. If, in the meantime, you're up for playing with
this a bit, feel free. :-D

Thanks and Regards,
Dario
--Â
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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