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From: Mel Gorman on 13 Apr 2010 12:10
On Wed, Apr 14, 2010 at 12:25:01AM +0900, Minchan Kim wrote:
> if node_state is N_HIGH_MEMORY, node doesn't have -1.

Also, if node_state is called with -1, a negative index is being checked in
a bitmap and that would be pretty broken in itself. I can't see a problem
with this patch.

Reviewed-by: Mel Gorman <mel(a)csn.ul.ie>

> It means node's validity check is unnecessary.
> So we can use alloc_pages_exact_node instead of alloc_pages_node.
> It could avoid comparison and branch as 6484eb3e2a81807722 tried.
>
> Cc: Christoph Lameter <cl(a)linux-foundation.org>
> Signed-off-by: Minchan Kim <minchan.kim(a)gmail.com>
> ---
> mm/sparse-vmemmap.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 392b9bb..7710ebc 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -53,7 +53,7 @@ void * __meminit vmemmap_alloc_block(unsigned long size, int node)
> struct page *page;
>
> if (node_state(node, N_HIGH_MEMORY))
> - page = alloc_pages_node(node,
> + page = alloc_pages_exact_node(node,
> GFP_KERNEL | __GFP_ZERO, get_order(size));
> else
> page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
> --
> 1.7.0.5
>

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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From: KAMEZAWA Hiroyuki on 13 Apr 2010 20:30
On Wed, 14 Apr 2010 00:25:01 +0900
Minchan Kim <minchan.kim(a)gmail.com> wrote:

> if node_state is N_HIGH_MEMORY, node doesn't have -1.
> It means node's validity check is unnecessary.
> So we can use alloc_pages_exact_node instead of alloc_pages_node.
> It could avoid comparison and branch as 6484eb3e2a81807722 tried.
>
> Cc: Christoph Lameter <cl(a)linux-foundation.org>
> Signed-off-by: Minchan Kim <minchan.kim(a)gmail.com>

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>

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