On Mon, Jul 2, 2012 at 7:54 PM, Jiang Liu [off-list ref] wrote:

On 2012-7-3 4:43, Yinghai Lu wrote:

quoted

On Sun, Jul 1, 2012 at 7:01 PM, Jiang Liu [off-list ref] wrote:

quoted

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 =91,=92 or =91;=92 before =91__att=

ribute__=92

quoted

quoted

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().

ah,  then use use _DEFAULT instead and later could update that in earlyp=

aram.

quoted

So attached -v2 should  work.

Hi Yinghai,

I'm afraid the v2 will break powerpc. Currently only IA64 and PowerPC
supports variable hugetlb size.

HPAGE_SHIFT is a variable default to 0 on powerpc. But seems PowerPC
is doing something wrong here, according to it's mm initialization
sequence as below:
start_kernel()
        setup_arch()
                paging_init()
                        free_area_init_node()
                                set_pageblock_order()
                                        refer to HPAGE_SHIFT (still 0)
        init_rest()
                do_initcalls()
                        hugetlbpage_init()
                                setup HPAGE_SHIFT
That means pageblock_order is always set to "MAX_ORDER - 1", not sure
whether this is intended. And it has the same issue as IA64 of wasting
memory if CONFIG_SPARSE is enabled.

adding BenH, need to know if it is powerpc intended.

So it would be better to keep function set_pageblock_order(), it will
fix the memory wasting on both IA64 and PowerPC.

Should setup pageblock_order as early as possible to avoid confusing.

Thanks

Yinghai