On Fri, 27 Jan 2023 17:23:39 +0100 David Hildenbrand <david@xxxxxxxxxx> wrote:
> On 26.01.23 23:27, Mike Kravetz wrote:
> > A hugetlb page will have a mapcount of 1 if mapped by multiple processes
> > via a shared PMD. This is because only the first process increases the
> > map count, and subsequent processes just add the shared PMD page to
> > their page table.
> >
> > page_mapcount is being used to decide if a hugetlb page is shared or
> > private in /proc/PID/smaps. Pages referenced via a shared PMD were
> > incorrectly being counted as private.
> >
> > To fix, check for a shared PMD if mapcount is 1. If a shared PMD is
> > found count the hugetlb page as shared. A new helper to check for a
> > shared PMD is added.
> >
> ...
>
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -749,8 +749,14 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
> >
> > if (mapcount >= 2)
> > mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
> > - else
> > - mss->private_hugetlb += huge_page_size(hstate_vma(vma));
> > + else {
>
> Better:
>
> if (mapcount >= 2 || hugetlb_pmd_shared(pte))
> mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
> else
> mss->private_hugetlb += huge_page_size(hstate_vma(vma));
Yup. And that local doesn't add any value?
--- a/fs/proc/task_mmu.c~mm-hugetlb-proc-check-for-hugetlb-shared-pmd-in-proc-pid-smaps-fix
+++ a/fs/proc/task_mmu.c
@@ -745,18 +745,10 @@ static int smaps_hugetlb_range(pte_t *pt
page = pfn_swap_entry_to_page(swpent);
}
if (page) {
- int mapcount = page_mapcount(page);
-
- if (mapcount >= 2)
+ if (page_mapcount(page) >= 2 || hugetlb_pmd_shared(pte))
mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
- else {
- if (hugetlb_pmd_shared(pte))
- mss->shared_hugetlb +=
- huge_page_size(hstate_vma(vma));
- else
- mss->private_hugetlb +=
- huge_page_size(hstate_vma(vma));
- }
+ else
+ mss->private_hugetlb += huge_page_size(hstate_vma(vma));
}
return 0;
}
_
