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

[Shaohua Li <shaohua.li@intel.com>]

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@linux-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 ...