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SubjectRe: [RFC] Obtaining memory information for kexec/kdump
Dave Hansen wrote:
> On Thu, 2005-03-24 at 11:19 +0530, Hariprasad Nellitheertha wrote:

> I think there's likely a lot of commonality with the needs of memory
> hotplug systems here. We effectively dump out the physical layout of
> the system, but in sysfs. We do this mostly because any memory hotplug
> changes generate hotplug events, just like all other hardware. If you
> do this in /proc, it's another thing that memory hotplug will have to
> update.

We put it in /proc primarily because what we wanted was
similar in many ways to /proc/iomem and so we (re)use a bit
of the code. Also, we were wondering if it is appropriate to
put in multiple values in a single file in sysfs.

> Also, we already have a concept of active and non-active physical
> memory: we call it online and offline. Some tweaks to the information
> that we export might be all that you need, instead of creating a new
> interface.

Looks like. And the tweaks could be handled by the user
space kexec-tools.

I've attached a document I started writing a couple days ago
> about the sysfs layout and the call paths for hotplug. It's horribly
> incomplete, but not a bad start.
> If you want to see some more details of the layout, please check out
> this patch set:

This does not have the sysfs related code. Is there a
separate patch for adding the sysfs entries?

> A good example of all of the hotplug stuff enabled for a normal machine
> is this .config, it boots on my 4-way PIII Xeon.
> You're welcome to borrow the machine that I normally boot this config
> on. Should make booting it relatively foolproof. :)
> -- Dave
> ------------------------------------------------------------------------
> block_size_bytes: The size of each memory section (in hex)

This value is per memoryXXXX directory, right?

Regards, Hari
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