linux-kernel - Re: [linux-pm] [PATCH] hibernation should work ok with memory hotplug

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Message-Id: <1225813182.12673.587.camel@nimitz>
Date:	Tue, 04 Nov 2008 07:39:42 -0800
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Nigel Cunningham <ncunningham@...a.org.au>,
	Matt Tolentino <matthew.e.tolentino@...el.com>,
	linux-pm@...ts.osdl.org, Dave Hansen <haveblue@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, pavel@...e.cz,
	Mel Gorman <mel@...net.ie>, Andy Whitcroft <apw@...dowen.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH] hibernation should work ok with memory
	hotplug

On Tue, 2008-11-04 at 16:35 +0100, Rafael J. Wysocki wrote:
> On Tuesday, 4 of November 2008, Dave Hansen wrote:
> > On Tue, 2008-11-04 at 09:54 +0100, Rafael J. Wysocki wrote:
> > > To handle this, I need to know two things:
> > > 1) what changes of the zones are possible due to memory hotplugging
> > > (i.e.    can they grow, shring, change boundaries etc.)
> > 
> > All of the above. 
> 
> OK
> 
> If I allocate a page frame corresponding to specific pfn, is it guaranteed to
> be associated with the same pfn in future?

Page allocation is different.  Since you hold a reference to a page, it
can not be removed until you release that reference.  That's why every
normal alloc_pages() user in the kernel doesn't have to worry about
memory hotplug.

> > Why walk zones instead of pgdats? 
> 
> This is a historical thing rather than anything else.  I think we could switch
> to pgdats, but that would require a code rewrite that's likely to introduce
> bugs, while our image-creating code is really well tested and doesn't change
> very often.

OK, fair enough.  I just wanted you to know that there are options other
than zones.

-- Dave

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