Re: [PATCH] mm/page_alloc: Skip non present sections on zone initialization

David Hildenbrand
2020-01-10T13:15:35Z

On 08.01.20 15:40, Michal Hocko wrote:
> On Mon 30-12-19 12:38:28, Kirill A. Shutemov wrote:
>> memmap_init_zone() can be called on the ranges with holes during the
>> boot. It will skip any non-valid PFNs one-by-one. It works fine as long
>> as holes are not too big.
>>
>> But huge holes in the memory map causes a problem. It takes over 20
>> seconds to walk 32TiB hole. x86-64 with 5-level paging allows for much
>> larger holes in the memory map which would practically hang the system.
>>
>> Deferred struct page init doesn't help here. It only works on the
>> present ranges.
>>
>> Skipping non-present sections would fix the issue.
>
> Makes sense to me.
>
>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>
> That pfn inc back and forth is quite ugly TBH but whatever.

Indeed, can we please rewrite the loop to fix that?

--
Thanks,

David / dhildenb