Hi Yinghai,
	The patch fails compilation as below:
mm/page_alloc.c:151: error: initializer element is not constant
mm/page_alloc.c:151: error: expected ?,? or ?;? before ?__attribute__?

On IA64, HUGETLB_PAGE_ORDER has dependency on variable hpage_shift.
# define HUGETLB_PAGE_ORDER        (HPAGE_SHIFT - PAGE_SHIFT)
# define HPAGE_SHIFT               hpage_shift

And hpage_shift could be changed by early parameter "hugepagesz".
So seems will still need to keep function set_pageblock_order().

Thanks!
Gerry

On 2012-7-1 4:15, Yinghai Lu wrote:

On Sat, Jun 30, 2012 at 2:07 AM, Jiang Liu [off-list ref] wrote:

quoted

From: Xishi Qiu <redacted>

On architectures with CONFIG_HUGETLB_PAGE_SIZE_VARIABLE set, such as Itanium,
pageblock_order is a variable with default value of 0. It's set to the right
value by set_pageblock_order() in function free_area_init_core().

But pageblock_order may be used by sparse_init() before free_area_init_core()
is called along path:
sparse_init()
   ->sparse_early_usemaps_alloc_node()
       ->usemap_size()
           ->SECTION_BLOCKFLAGS_BITS
               ->((1UL << (PFN_SECTION_SHIFT - pageblock_order)) *
NR_PAGEBLOCK_BITS)

The uninitialized pageblock_size will cause memory wasting because usemap_size()
returns a much bigger value then it's really needed.

For example, on an Itanium platform,
sparse_init() pageblock_order=0 usemap_size=24576
free_area_init_core() before pageblock_order=0, usemap_size=24576
free_area_init_core() after pageblock_order=12, usemap_size=8

That means 24K memory has been wasted for each section, so fix it by calling
set_pageblock_order() from sparse_init().

can you check attached patch?

That will kill more lines code instead.

Thanks

Yinghai

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