David Rientjes wrote:
> Currently, thp_fault_fallback in vmstat only gets incremented if a
> hugepage allocation fails. If current's memcg hits its limit or the page
> fault handler returns an error, it is incorrectly accounted as a
> successful thp_fault_alloc.
>
> Count thp_fault_fallback anytime the page fault handler falls back to
> using regular pages and only count thp_fault_alloc when a hugepage has
> actually been faulted.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
It's probably a good idea, but please make the behaviour consistent in
do_huge_pmd_wp_page() and collapse path, otherwise it doesn't make sense.
And please make the patch against mm tree: do_huge_pmd_anonymous_page()
was modified recently.
> ---
> mm/huge_memory.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -801,7 +801,6 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
> zero_page = get_huge_zero_page();
> if (unlikely(!zero_page)) {
> pte_free(mm, pgtable);
> - count_vm_event(THP_FAULT_FALLBACK);
> goto out;
> }
> spin_lock(&mm->page_table_lock);
> @@ -816,11 +815,8 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
> }
> page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
> vma, haddr, numa_node_id(), 0);
> - if (unlikely(!page)) {
> - count_vm_event(THP_FAULT_FALLBACK);
> + if (unlikely(!page))
> goto out;
> - }
> - count_vm_event(THP_FAULT_ALLOC);
> if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
> put_page(page);
> goto out;
> @@ -832,9 +828,11 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
> goto out;
> }
>
> + count_vm_event(THP_FAULT_ALLOC);
> return 0;
> }
> out:
> + count_vm_event(THP_FAULT_FALLBACK);
> /*
> * Use __pte_alloc instead of pte_alloc_map, because we can't
> * run pte_offset_map on the pmd, if an huge pmd could
--
Kirill A. Shutemov
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