On 20/04/16 00:59, Aneesh Kumar K.V wrote:

Michael Ellerman [off-list ref] writes:

quoted

On Fri, 2016-19-02 at 05:38:47 UTC, Rashmica Gupta wrote:

quoted

Currently on PPC64 changing kernel pagesize from 4K to 64K leaves
FORCE_MAX_ZONEORDER set to 13 - which produces a compile error.

...

quoted

So, update the range of FORCE_MAX_ZONEORDER from 9-64 to 8-9 for 64K pages
and from 13-64 to 9-13 for 4K pages.

Signed-off-by: Rashmica Gupta <redacted>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/a7ee539584acf4a565b7439cea

HPAGE_PMD_ORDER is not something we should check w.r.t 4k linux page
size. We do have the below constraint w.r.t hugetlb pages

static inline bool hstate_is_gigantic(struct hstate *h)
{
	return huge_page_order(h) >= MAX_ORDER;
}

That require MAX_ORDER to be greater than 12.

The build will fail for MAX_ZONEORDER beyond the specified limits.
MAX_ORDER > 12 for what page size?

My understanding is this

1. gigantic refers to the fact the regular allocators cannot allocate
this page
2. Use alloc_contig_range() with CONFIG_CMA for gigantic pages

I could be wrong

Did we test hugetlbfs 4k config with this patch ? Will it work if we
start marking hugepage as gigantic page ?

Nope.. I did not

Thanks for the review!
Balbir Singh