Re: [PATCH v8 02/14] mm/gup: check every subpage of a compound page during isolation

On 2/3/21 3:32 PM, Joao Martins wrote:

On 2/3/21 2:51 PM, Pavel Tatashin wrote:

...

On Wed, Feb 3, 2021 at 8:23 AM Joao Martins joao.m.martins@oracle.com wrote:

...

On 1/25/21 7:47 PM, Pavel Tatashin wrote: for compound pages but when !is_transparent_hugepage(head) or just PageHuge(head) like:

•           if (!is_transparent_hugepage(head) && PageCompound(page))
  

•                   i += (compound_nr(head) - (pages[i] - head));
  
  

Or making specific to hugetlbfs:

•           if (PageHuge(head))
  

•                   i += (compound_nr(head) - (pages[i] - head));
  

Yes, this is reasonable optimization. I will submit a follow up patch against linux-next.

Realized it late, but the previous step was already broken. And I inherited its brokeness, when copy-pasting the deleted chunk:

The @step should be capped at the remaining pages to iterate:

i += min(nr_pages - i, compound_nr(head) - (pages[i] - head));

Joao