Re: [PATCHv6 01/36] mm, proc: adjust PSS calculation

Vlastimil Babka
2015-06-09T12:29:30Z

On 06/03/2015 07:05 PM, Kirill A. Shutemov wrote:
> With new refcounting all subpages of the compound page are not nessessary
> have the same mapcount. We need to take into account mapcount of every
> sub-page.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Tested-by: Sasha Levin <sasha.levin@oracle.com>
> Acked-by: Jerome Marchand <jmarchan@redhat.com>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> fs/proc/task_mmu.c | 48 +++++++++++++++++++++++++++++++-----------------
> 1 file changed, 31 insertions(+), 17 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 58be92e11939..f9b285761bc0 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -449,9 +449,10 @@ struct mem_size_stats {
> };
>
> static void smaps_account(struct mem_size_stats *mss, struct page *page,
> - unsigned long size, bool young, bool dirty)
> + bool compound, bool young, bool dirty)
> {
> - int mapcount;
> + int i, nr = compound ? HPAGE_PMD_NR : 1;
> + unsigned long size = nr * PAGE_SIZE;
>
> if (PageAnon(page))
> mss->anonymous += size;
> @@ -460,23 +461,36 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
> /* Accumulate the size in pages that have been accessed. */
> if (young || PageReferenced(page))
> mss->referenced += size;
> - mapcount = page_mapcount(page);
> - if (mapcount >= 2) {
> - u64 pss_delta;
>
> - if (dirty || PageDirty(page))
> - mss->shared_dirty += size;
> - else
> - mss->shared_clean += size;
> - pss_delta = (u64)size << PSS_SHIFT;
> - do_div(pss_delta, mapcount);
> - mss->pss += pss_delta;
> - } else {
> + /*
> + * page_count(page) == 1 guarantees the page is mapped exactly once.
> + * If any subpage of the compound page mapped with PTE it would elevate
> + * page_count().
> + */
> + if (page_count(page) == 1) {
> if (dirty || PageDirty(page))
> mss->private_dirty += size;
> else
> mss->private_clean += size;
> - mss->pss += (u64)size << PSS_SHIFT;

Deleting the line above was a mistake, right?

> + return;
> + }
> +
> + for (i = 0; i < nr; i++, page++) {
> + int mapcount = page_mapcount(page);
> +
> + if (mapcount >= 2) {
> + if (dirty || PageDirty(page))
> + mss->shared_dirty += PAGE_SIZE;
> + else
> + mss->shared_clean += PAGE_SIZE;
> + mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
> + } else {
> + if (dirty || PageDirty(page))
> + mss->private_dirty += PAGE_SIZE;
> + else
> + mss->private_clean += PAGE_SIZE;
> + mss->pss += PAGE_SIZE << PSS_SHIFT;
> + }
> }
> }
>
> @@ -500,7 +514,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
>
> if (!page)
> return;
> - smaps_account(mss, page, PAGE_SIZE, pte_young(*pte), pte_dirty(*pte));
> +
> + smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte));
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> @@ -516,8 +531,7 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
> if (IS_ERR_OR_NULL(page))
> return;
> mss->anonymous_thp += HPAGE_PMD_SIZE;
> - smaps_account(mss, page, HPAGE_PMD_SIZE,
> - pmd_young(*pmd), pmd_dirty(*pmd));
> + smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd));
> }
> #else
> static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
>