On 09/14/22 13:58, Andrew Morton wrote:
> On Wed, 14 Sep 2022 10:23:05 -0700 Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
>
> > On 09/13/22 12:54, Doug Berger wrote:
> > > When demoting a hugepage to a smaller order, the number of pages
> > > added to the target hstate will be the size of the large page
> > > divided by the size of the smaller page.
> > >
> > > Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support")
> > > Signed-off-by: Doug Berger <opendmb@xxxxxxxxx>
> > > ---
> > > mm/hugetlb.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > > index e070b8593b37..79949893ac12 100644
> > > --- a/mm/hugetlb.c
> > > +++ b/mm/hugetlb.c
> > > @@ -3472,7 +3472,8 @@ static int demote_free_huge_page(struct hstate *h, struct page *page)
> > > * based on pool changes for the demoted page.
> > > */
> > > h->max_huge_pages--;
> > > - target_hstate->max_huge_pages += pages_per_huge_page(h);
> > > + target_hstate->max_huge_pages += pages_per_huge_page(h) /
> > > + pages_per_huge_page(target_hstate);
> > >
> > > return rc;
> > > }
> >
> > This has already been fixed here,
> >
> > https://lore.kernel.org/linux-mm/20220823030209.57434-2-linmiaohe@xxxxxxxxxx/
>
> Neither version tells us the user-visible runtime effects of the change :(
Sorry, I should have pushed harder on this with Miaohe's patch.
There are no user-visible runtime effects. In fact, this change really causes
no functional change (unless I am mistaken and Miaohe did not correct me).
max_huge_pages is not used again until it is reset. See my explanation at:
https://lore.kernel.org/linux-mm/YvwfvxXewnZpHQcz@monkey/
--
Mike Kravetz
