linux-kernel - Re: + memory-hotplug-alloc-page-from-other-node-in-memory-online.patch added to -mm tree

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Date:	Wed, 1 Jul 2009 10:55:58 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mel@....ul.ie" <mel@....ul.ie>,
	"Zhao, Yakui" <yakui.zhao@...el.com>
Subject: Re: +
	memory-hotplug-alloc-page-from-other-node-in-memory-online.patch
	added to -mm tree

On Tue, Jun 30, 2009 at 08:47:35AM +0800, Shaohua Li wrote:
> On Tue, Jun 30, 2009 at 06:07:16AM +0800, Christoph Lameter wrote:
> > On Mon, 29 Jun 2009, akpm@...ux-foundation.org wrote:
> > 
> > > To initialize hotadded node, some pages are allocated.  At that time, the
> > > node hasn't memory, this makes the allocation always fail.  In such case,
> > > let's allocate pages from other nodes.
> > 
> > Thats bad. Could you populate the buddy list with some large pages from
> > the  beginning of the node instead of doing this special casing? The
> > vmemmap and other stuff really should come from the node that is added.
> > Otherwise off node memory accesses will occur constantly for processors on
> > that node.
> Ok, this is preferred. But the node hasn't any memory present at that time,
> let me check how could we do it.
Hi Christoph,
Looks this is quite hard. Memory of the node isn't added into buddy. At that
time (sparse-vmmem init) buddy for the node isn't initialized and even page struct
for the hotadded memory isn't prepared too. We need something like bootmem
allocator to get memory ...
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