On 2022/8/17 7:34, Mike Kravetz wrote: > 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. Many thanks both. I will try to do this "more extensive cleanup" after pending work is done. Thanks, Miaohe Lin
