linux-kernel - Re: Trying to make use of hotplug memory for xen balloon driver

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Date:	Wed, 26 Mar 2008 17:26:35 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Yasunori Goto <y-goto@...fujitsu.com>,
	Christoph Lameter <clameter@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Anthony Liguori <anthony@...emonkey.ws>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: Trying to make use of hotplug memory for xen balloon driver

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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