Re: Strange interdependace between domains

[Dario Faggioli <dario.faggioli@citrix.com>]

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On lun, 2014-02-17 at 09:13 -0500, Nate Studer wrote:
> On 2/14/2014 12:21 PM, Dario Faggioli wrote:

> > All this to say that, it should be possible to get a bit more of
> > isolation, by tweaking the proper Xen code path appropriately, but if
> > the amount of interference that comes from two hypethreads sharing
> > registers, pipeline stages, and whatever it is that they share, is
> > enough for disturbing your workload, then, I'm afraid we never get much
> > farther from the 'don't use hyperthread' solution! :-(
> 
> Which, as you say, unfortunately is the solution unless there is some way to
> configure the hardware to eliminate this interference.  
>
Yeah, I know!

> If it's any consolation,
> the only multi-core ARINC653 implementations I know of have enacted these two
> restrictions:
> 1.  # of cores enabled = # of memory controllers.
> 2.  Each enabled core must be configured to not share a memory controller,
> cache, registers, etc...
> 
Nice. :-)

> It is practically an AMP system at that point, but without these restrictions
> you can get some unpredictable behavior unless you have some specialized or
> exotic hardware to make things more deterministic.
> 
Sure, when you really need to be serious about isolation, treats are
there well before software (whatever is just OS, virt, whatever) comes
into play!

Thanks for sharing this and 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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