On 06/19/2018 11:08 PM, Yang Shi wrote:
> Since commit eca56ff906bdd0239485e8b47154a6e73dd9a2f3 ("mm, shmem: add
> internal shmem resident memory accounting"), MM_SHMEMPAGES is added to
> separate the shmem accounting from regular files. So, all shmem pages
> should be accounted to MM_SHMEMPAGES instead of MM_FILEPAGES.
>
> And, normal 4K shmem pages have been accounted to MM_SHMEMPAGES, so
> shmem thp pages should be not treated differently. Accouting them to
> MM_SHMEMPAGES via mm_counter_file() since shmem pages are swap backed
> to keep consistent with normal 4K shmem pages.
>
> This will not change the rss counter of processes since shmem pages are
> still a part of it.
<Andrew>So what are the user-visible effects of the patch then?</Andrew>
Let's add this?:
The /proc/pid/status and /proc/pid/statm counters will however be more
accurate wrt shmem usage, as originally intended.
> Signed-off-by: Yang Shi <[email protected]>
> Cc: Hugh Dickins <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
Good catch, thanks. I guess the discrepancy happened due to the
thp-tmpfs patchset existing externally for a long time and number of
iterations, while commit eca56ff906bdd was merged, and nobody noticed
that the thp case added more MM_FILEPAGES users.
Acked-by: Vlastimil Babka <[email protected]>
> ---
> mm/huge_memory.c | 4 ++--
> mm/memory.c | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 1cd7c1a..2687f7c 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1740,7 +1740,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct
> vm_area_struct *vma,
> } else {
> if (arch_needs_pgtable_deposit())
> zap_deposited_table(tlb->mm, pmd);
> - add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
> + add_mm_counter(tlb->mm, mm_counter_file(page),
> -HPAGE_PMD_NR);
> }
>
> spin_unlock(ptl);
> @@ -2088,7 +2088,7 @@ static void __split_huge_pmd_locked(struct
> vm_area_struct *vma, pmd_t *pmd,
> SetPageReferenced(page);
> page_remove_rmap(page, true);
> put_page(page);
> - add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
> + add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
> return;
> } else if (is_huge_zero_pmd(*pmd)) {
> /*
> diff --git a/mm/memory.c b/mm/memory.c
> index 7206a63..4a2f2a8 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3372,7 +3372,7 @@ static int do_set_pmd(struct vm_fault *vmf, struct page
> *page)
> if (write)
> entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
>
> - add_mm_counter(vma->vm_mm, MM_FILEPAGES, HPAGE_PMD_NR);
> + add_mm_counter(vma->vm_mm, mm_counter_file(page), HPAGE_PMD_NR);
> page_add_file_rmap(page, true);
> /*
> * deposit and withdraw with pmd lock held
>
