Re: [Xen-devel] Xen on ARM IRQ latency and scheduler overhead

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Fri, 2017-02-17 at 16:02 -0800, Stefano Stabellini wrote:
> On Fri, 17 Feb 2017, Stefano Stabellini wrote:
> > 
> > NODEBUG vwfi=idle credit2 fix cpumasks      4000    2370    
> > 4500        3350
> > NODEBUG vwfi=idle credit1 fix cpumasks      3220    2180    
> > 4500        4320
> 
> Actually those are still the old numbers, sorry! 
>
Yeah, I know, I've done the same sooo many times! :-P

> I didn't update the xen
> binary properly. These are the new numbers:
> 
>                                   AVG     MIN     MAX
>           WARM MAX
> vwfi=sleep credit2 fix cpumasks       5910    5800    8520    
> 6180
> vwfi=sleep credit1 fix cpumasks       4900    4810    6910    
> 4980
> vwfi=idle  credit2 fix cpumasks       2800    1560    4550    
> 4200
> vwfi=idle  credit1 fix cpumasks       2800    1610    3420    
> 1770
> 
> The difference between credit2 and credit1 is smaller now. In fact
> it's
> zero, when vwfi=idle. 
>
Ok, cool.

> However, with vwfi=sleep, the larger MAX value is
> a bit worrying.
> 
I still think this may be due to the fact that you never stop Credit1's
tick on ARM, which means that, when on Credit1, the system is a lot
more "alive" (e.g., if we were on x86, I'd have said it'd spend less
time in deep C-states, and things like that).

And yes, I still owe you a patch for disabling it.
I'm working on that one. :-)

Regards,
Dario
-- 
<<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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