linux-kernel - Re: [PATCH RFC] hotplug-memory: refactor online_pages to separate zone growth from page onlining

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Message-Id: <20080403160316.c341bc0e.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 3 Apr 2008 16:03:16 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Dave Hansen <dave@...ux.vnet.ibm.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>,
	Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH RFC] hotplug-memory: refactor online_pages to separate
 zone growth from page onlining

On Wed, 02 Apr 2008 15:13:05 -0700
Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> > Yeah, but I'm just talking about hotplugged memory.  When we add it, we
> > don't have to map the added pages (since they're highmem) and don't have
> > to touch their contents and zero them out, either.  Then, the balloon
> > driver can notice that the memory is too large, and start to balloon it
> > down.
> >   
> 
> I didn't think x86-64 had a notion of highmem.
> 
> How do you prevent the pages from being used before they're ballooned out?
> 

As I mentioned before, you can do that by plug online_page().

Now, online_page() is per-architecture. So, it's not so bad to make this
online_page() to be just a callback.
=
int online_page(struct page *page)
{
	if (online_page_callback)
		return (*online_page_callback)(struct page *page);
	retrun arch_default_online_page(page);
}
=
maybe not so dirty look. 

your ballon driver can overwrite this callback pointer.

Thanks,
-Kame

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