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SubjectRe: [RFC] Obtaining memory information for kexec/kdump
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On Thu, 2005-03-24 at 15:49 +0530, Hariprasad Nellitheertha wrote:
> Dave Hansen 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.

The code reuse is nice, but the expanded use of /proc is not.

> Also, we were wondering if it is appropriate to
> put in multiple values in a single file in sysfs.

Why would you need to do that?
> 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:
> >
> > http://www.sr71.net/patches/2.6.12/2.6.12-rc1-mhp1/patch-2.6.12-rc1-mhp1.gz
>
> This does not have the sysfs related code. Is there a
> separate patch for adding the sysfs entries?

Hmmm. I think my rollup script broke. Try this:

http://www.sr71.net/patches/2.6.12/2.6.12-rc1-mhp1/broken-out/L0-sysfs-memory-class.patch

> > block_size_bytes: The size of each memory section (in hex)
>
> This value is per memoryXXXX directory, right?

No, it's global. However, we have discussed doing it per-section in the
future to collapse some of the contiguous areas into a single directory.

-- Dave

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