Re: [XenARM] [Android-virt] [ANNOUNCE] Xvisor ARM better than KVM ARM in CPU virtualization

[Marc Zyngier <marc.zyngier@xxxxxxx>]

On Sat, 5 May 2012 15:24:26 +0100
Anup Patel <anup@xxxxxxxxxxxxxx> wrote:

> Hi PMM,
> 
> I agree we cannot predict real world performance based on performance on ARM 
> fast models but if system A is performing better than system B no ARM fast 
> model or QEMU then in real world system A will perform better than system B. 
> Of-course in real world scale of difference in performance between system A 
> and system B will differ.
> 

You may want to re-read Peter's email, and consider that the model
doesn't represent the micro-architecture. A code sequence X can be
faster than a sequence Y on the model, and the opposite on real
hardware. The same is equally valid on two different implementation of
the same architecture (Cortex-A7 vs Cortex-A15, for example).

> The previous announcement only proves that Xvisor ARM is relatively better 
> than KVM ARM.

On the Fast Model.

        M.
 
> On Sat, May 5, 2012 at 3:36 PM, Peter Maydell 
> <peter.maydell@xxxxxxxxxx<mailto:peter.maydell@xxxxxxxxxx>> wrote:
> 2012/5/5 Anup Patel <anup@xxxxxxxxxxxxxx<mailto:anup@xxxxxxxxxxxxxx>>:
> > This announcement is to show an apple to apple performance comparison
> > between Xvisor ARM and KVM ARM running on VExpress-A15 Fast Model.
> 
> I would strongly caution against trying to do any performance/timing
> type tests if you're still running on the ARM Fast Model -- they are
> not representative of performance characteristics on hardware
> and you really can't draw any conclusions about real world
> performance by timing things on a model. It's quite easy to get
> into a situation where all you're measuring is "does my code happen
> to do a lot of some perfectly reasonable operation which happens
> to be hard and slow to implement for the model?".
> 
> (Also, KVM for ARM is still under development and we haven't
> yet made several of the obvious performance improvements like
> in-kernel irqchip and timer support, so it's not really a very
> useful thing to compare against yet.)
> 
> -- PMM
> 



-- 
I'm the slime oozin' out from your TV set...


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