Re: [ANNOUNCE] [PATCH] Node Hotplug Support

From: Andi Kleen
Date: Mon May 10 2004 - 14:58:15 EST

On Mon, May 10, 2004 at 11:17:22AM +0900, Keiichiro Tokunaga wrote:
> As you mentioned, there can be many more things. However,
> the examples you showed should be handled by individual hotplug.
> For instance, the processes bound to a certain CPU should be
> handled by CPU hotplug when node hotplug invokes CPU hotplug.
> Also, the device drivers bound to slots should be detached by
> IO hotplug. Node hotplug is supposed to take care of a container
> device and just invoke individual hotplugs for other devices.
> Node hotplug doesn't break any policy of each hotplug (CPU,
> memory, IO, etc).

To coordinate all them you need user space infrastructure anyways
that knows about all the elements of a node. I don't see why you want a
kernel level container too; userspace can do this job already
and would be much more flexible.

> > This has the advantage that if there is some reason to
> > add CPUs without memory (or memory without CPUs or PCI slots
> > without anything) it will just work too. It is not clear
> > that your "lump everything mechanism into one" can handle all
> > that. Most likely you would need to add lots of special
> > cases to it to handle all this. Separate mechanisms can
> > do this cleaner.
> Yes. The cases (combination of hardware) would increase.
> However, I don't think there would be that many today.

I am mainly thinking about virtualization here for which hotplug
of everything makes definitely sense. But the requirements could
be very different from what a big iron machine wants.

> Are you saying here that platform-independent and dependent
> codes should be separated so that the independent part could
> be implemented by any other platform (firmware) in their own
> style? If so, I agree and some discussion are necessary :)


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