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Re: [Xen-devel] Implement 3-level event channel routines in Linux.

On Wed, 2013-01-02 at 18:26 +0000, Konrad Rzeszutek Wilk wrote:
> On Mon, Dec 31, 2012 at 06:38:54PM +0000, Wei Liu wrote:
> > This patch series implements 3-level event channel routines in Linux kernel.
> > 
> > My thought is that 3-level event channel is only useful for Dom0 or driver
> > domain, so it is not enabled by default. Enable it with evtchn_level=3 in
> > kernel command line.
> Could it be enabled dynamically? Say when we are close to exhausting the
> amount of channels? Or if the machine has some large amount of memory and
> hence would probably allocate many many guests?

Do you mean enabling this mechanism on the fly when Dom0 / driver domain
is running? Or do you mean enabling it based on some metrics when
starting up a domain?

If it is the first case, who is responsible for initiating the switching
process? It looks like it is Xen's responsibility to do the switch
because Dom0 sometimes cannot know the true capability of underlying
hardware. If it is Xen, then we need to add callback to poke Dom0 /
driver domain.

For both cases, what do you have in mind for the metric that used to
trigger the switch? How much RAM / how many CPUs is the threshold?


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