On Wed, Dec 05, 2018 at 11:15:13AM +0000, Mel Gorman wrote:
>On Wed, Dec 05, 2018 at 05:19:04PM +0800, Wei Yang wrote:
>> When SPARSEMEM is used, there is an indication that pageblock is not
>> allowed to exceed one mem_section. Current code doesn't have this
>> constrain explicitly.
>>
>> This patch adds this to make sure it won't.
>>
>> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
>
>Is this even possible? This would imply that the section size is smaller
>than max order which would be quite a crazy selection for a sparesemem
>section size. A lot of assumptions on the validity of PFNs within a
>max-order boundary would be broken with such a section size. I'd be
>surprised if such a setup could even boot, let alone run.
pageblock_order has two definitions.
#define pageblock_order HUGETLB_PAGE_ORDER
#define pageblock_order (MAX_ORDER-1)
If CONFIG_HUGETLB_PAGE is not enabled, pageblock_order is related to
MAX_ORDER, which ensures it is smaller than section size.
If CONFIG_HUGETLB_PAGE is enabled, pageblock_order is not related to
MAX_ORDER. I don't see HUGETLB_PAGE_ORDER is ensured to be less than
section size. Maybe I missed it?
>
>--
>Mel Gorman
>SUSE Labs
--
Wei Yang
Help you, Help me
