Subject: Re: Trying to make use of hotplug memory for xen balloon driver
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Yasunori Goto <y-goto@jp.fujitsu.com>,
       Christoph Lameter <clameter@sgi.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Anthony Liguori <anthony@codemonkey.ws>,
       Chris Wright <chrisw@sous-sol.org>
In-Reply-To: <47EAD83A.2000000@goop.org>
References: <47EAD83A.2000000@goop.org>
Content-Type: text/plain
Date: Wed, 26 Mar 2008 17:26:35 -0700
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On Wed, 2008-03-26 at 16:11 -0700, Jeremy Fitzhardinge wrote:
>       Bad page state in process 'events/0'
>       page:c16fa0cc flags:0x00000000 mapping:00000000 mapcount:1 count:0
>       Trying to fix it up, but a reboot is needed

The flags being all null looks highly suspicious to me.

Once you've done an add_memory(), the new sections should show up
in /sys.  Do you see them in there?

Once they show up, you can online them with:

	echo online > /sys/devices/system/memory/memoryXXX/state

That's what actually goes and mucks with the 'struct zone's and the
pgdats to expand them.  It will also call online_page() on the whole
range.  I think you're trying to do this manually, and missing part of
it.  

There's some documentation here:

http://kerneltrap.org/node/14009

But, think of it this way: "add" is what the hardware does.  "online" is
what Linux does after the memory has been added so that it can be used.

-- Dave

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