Re: [RFC v2 PATCH] mm: shmem: make stat.st_blksize return huge page size if THP is on

From: Michal Hocko
Date: Mon Apr 23 2018 - 11:04:49 EST


On Sun 22-04-18 21:28:59, Yang Shi wrote:
>
>
> On 4/22/18 6:47 PM, Michal Hocko wrote:
[...]
> > will be used on the first aligned address even when the initial/last
> > portion of the mapping is not THP aligned.
>
> No, my test shows it is not. And, transhuge_vma_suitable() does check the
> virtual address alignment. If it is not huge page size aligned, it will not
> set PMD for huge page.

It's been quite some time since I've looked at that code but I think you
are wrong. It just doesn't make sense to make the THP decision on the
VMA alignment much. Kirill, can you clarify please?

Please note that I have no objections to actually export the huge page
size as the max block size but your changelog just doesn't make any
sense to me.
--
Michal Hocko
SUSE Labs