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Re: [Xen-ia64-devel] Event channel vs current scheme speed [wasvIOSAPIC

To: "Dong, Eddie" <eddie.dong@xxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Magenheimer, Dan \(HP Labs Fort Collins\)" <dan.magenheimer@xxxxxx>, <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-ia64-devel] Event channel vs current scheme speed [wasvIOSAPIC and IRQs delivery]
From: Tristan Gingold <Tristan.Gingold@xxxxxxxx>
Date: Fri, 10 Mar 2006 16:28:55 +0100
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Le Vendredi 10 Mars 2006 16:01, Dong, Eddie a écrit :
> > I agree the current model has implicit priorities.
> >
> > But I am a little bit skeptical how the priority argument.  As far as
> > I understand, in Xen or in Linux first asked is first priority.
Sorry, I was not clear enough.  I agree event channel can mostly respect 
priority.

Except clock and IPI, I think Linux doesn't use priority.  I can't force a 
card to have an higher priority than another card.
Is it right ?

[...]
> These are all corner cases that we must consider as product, but at
> early development we can take shortcut like using pseudo IRQ for event
> channel here to let the whole project go ahead. And this is what we
> talked at xensummit, people (Dan, Ian, Keir, Jun) all have no object for
> potential issue concerns (for example mask/unmask support and priority
> issue) and agree to take next. PPC guy also uses pseudo physical IRQ for
> event channel as I remembered. Their community is much smaller than us
> now and their development is also lagger than IA64.
> This is why we need to clean up now as callback based event channel
> approach has already been in production stage. Making a new mechanism
> has high risk.
You know we don't agree on these points.  Writing them again won't make me 
change.

Tristan.


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