linux-kernel - Re: [Xen-devel] [PATCH 07/10] xen/mmu: Work with 1-1 mappings when allocating new top/middle entries.

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Message-ID: <20101222174728.GA24483@dumpdata.com>
Date:	Wed, 22 Dec 2010 12:47:28 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jeremy@...p.org" <jeremy@...p.org>,
	"hpa@...or.com" <hpa@...or.com>,
	Konrad Rzeszutek Wilk <konrad@...nel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Jan Beulich <JBeulich@...ell.com>
Subject: Re: [Xen-devel] [PATCH 07/10] xen/mmu: Work with 1-1 mappings when
 allocating new top/middle entries.

On Wed, Dec 22, 2010 at 08:54:31AM +0000, Ian Campbell wrote:
> On Tue, 2010-12-21 at 21:37 +0000, Konrad Rzeszutek Wilk wrote: 
> > We were not properly taking under advisement the 1-1 mappings
> > when a large area of memory was ballooned out.
> 
> Are we lazily allocating the p2m tree nodes for regions initially
> covered by the balloon? (perhaps we have always done this and it isn't
> new with this series)

Before: Yes
Now: Yes.
> 
> Would it be simpley to always populate enough tree nodes to cover the
> ballooned area as well as nr_pages at start of day and therefore avoid
> worrying about it later on (except for memory hotplug which is special
> in this way already)?

Tried that, ran out of reserved_brk space :-) But not sure what
we would gain for this - it is not always guaranteed that we will populate
up to the memory 'maxmem' region.

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