Subject: Re: [RFC] Obtaining memory information for kexec/kdump
From: Dave Hansen <haveblue@us.ibm.com>
To: "Hariprasad Nellitheertha [imap]" <hari@in.ibm.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       fastboot <fastboot@lists.osdl.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Andrew Morton <akpm@osdl.org>
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Date: Thu, 24 Mar 2005 07:32:51 -0800
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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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