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

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Date:	Fri, 28 Mar 2008 11:21:16 -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 Thu, 2008-03-27 at 15:23 -0700, Jeremy Fitzhardinge wrote:
> If the user does a mass online via /sys the system explodes because it
> onlines a large number of pages which have no backing memory.  Since 
> none of those pages can be mapped, the kernel explodes in a variety of
> interesting ways.

Yeah, it does look like you need some kind of partial onlining.

> So I'd really like to inhibit the sysfs interface on these sections.  
> Thoughts?

The balloon driver isn't an exact fit for memory hotplug as it stands,
so there are going to be a few growing pains here. :)

I'm not sure just inhibiting sysfs is the best thing.  What would you
think about adding partial sections, initializing the 'struct page's,
but just not touching the memory?

-- Dave

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