On 08/16/22 16:20, Andrew Morton wrote: > On Tue, 16 Aug 2022 15:52:47 -0700 Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote: > > > On 08/16/22 21:05, Miaohe Lin wrote: > > > There should be pages_per_huge_page(h) / pages_per_huge_page(target_hstate) > > > pages incremented for target_hstate->max_huge_pages when page is demoted. > > > Update max_huge_pages accordingly for consistency. > > > > > > Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> > > > --- > > > mm/hugetlb.c | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > > index ea1c7bfa1cc3..e72052964fb5 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); > > > > Thanks! > > > > That is indeed incorrect. However the miscalculation should not have any > > consequences. Correct? The value is used when initially populating the > > pools. It is never read and used again. It is written to in > > set_max_huge_pages if someone changes the number of hugetlb pages. > > > > I guess that is a long way of saying I am not sure why we care about trying > > to keep max_huge_pages up to date? I do not think it matters. > > > > I also thought, if we are going to adjust max_huge_pages here we may > > also want to adjust the node specific value: h->max_huge_pages_node[node]. > > There are a few other places where the global max_huge_pages is adjusted > > without adjusting the node specific value. > > > > The more I think about it, the more I think we should explore just > > eliminating any adjustment of this/these values after initially > > populating the pools. > > I'm thinking we should fix something that is "indeed incorrect" before > going on to more extensive things? Sure, I am good with that. Just wanted to point out that the incorrect calculation does not have any negative consequences. Maybe prompting Miaohe to look into the more extensive cleanup. -- Mike Kravetz
