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SubjectRe: [RFC][PATCH 3/6] break out smaps_pte_entry() from smaps_pte_range()
On Mon, 31 Jan 2011, Dave Hansen wrote:

>
> We will use smaps_pte_entry() in a moment to handle both small
> and transparent large pages. But, we must break it out of
> smaps_pte_range() first.
>

The extraction from smaps_pte_range() looks good. What's the performance
impact on very frequent consumers of /proc/pid/smaps, though, as the
result of the calls throughout the iteration if smaps_pte_entry() doesn't
get inlined (supposedly because you'll be reusing the extracted function
again elsewhere)?

>
> ---
>
> linux-2.6.git-dave/fs/proc/task_mmu.c | 85 ++++++++++++++++++----------------
> 1 file changed, 46 insertions(+), 39 deletions(-)
>
> diff -puN fs/proc/task_mmu.c~break-out-smaps_pte_entry fs/proc/task_mmu.c
> --- linux-2.6.git/fs/proc/task_mmu.c~break-out-smaps_pte_entry 2011-01-27 11:03:06.761548697 -0800
> +++ linux-2.6.git-dave/fs/proc/task_mmu.c 2011-01-27 11:03:06.773548685 -0800
> @@ -333,56 +333,63 @@ struct mem_size_stats {
> u64 pss;
> };
>
> -static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> - struct mm_walk *walk)
> +
> +static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> + struct mm_walk *walk)
> {
> struct mem_size_stats *mss = walk->private;
> struct vm_area_struct *vma = mss->vma;
> - pte_t *pte, ptent;
> - spinlock_t *ptl;
> struct page *page;
> int mapcount;
>
> - split_huge_page_pmd(walk->mm, pmd);
> -
> - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> - for (; addr != end; pte++, addr += PAGE_SIZE) {
> - ptent = *pte;
> + if (is_swap_pte(ptent)) {
> + mss->swap += PAGE_SIZE;
> + return;
> + }
>
> - if (is_swap_pte(ptent)) {
> - mss->swap += PAGE_SIZE;
> - continue;
> - }
> + if (!pte_present(ptent))
> + return;
>
> - if (!pte_present(ptent))
> - continue;
> + page = vm_normal_page(vma, addr, ptent);
> + if (!page)
> + return;
> +
> + if (PageAnon(page))
> + mss->anonymous += PAGE_SIZE;
> +
> + mss->resident += PAGE_SIZE;
> + /* Accumulate the size in pages that have been accessed. */
> + if (pte_young(ptent) || PageReferenced(page))
> + mss->referenced += PAGE_SIZE;
> + mapcount = page_mapcount(page);
> + if (mapcount >= 2) {
> + if (pte_dirty(ptent) || PageDirty(page))
> + mss->shared_dirty += PAGE_SIZE;
> + else
> + mss->shared_clean += PAGE_SIZE;
> + mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
> + } else {
> + if (pte_dirty(ptent) || PageDirty(page))
> + mss->private_dirty += PAGE_SIZE;
> + else
> + mss->private_clean += PAGE_SIZE;
> + mss->pss += (PAGE_SIZE << PSS_SHIFT);
> + }
> +}
>
> - page = vm_normal_page(vma, addr, ptent);
> - if (!page)
> - continue;
> +static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> + struct mm_walk *walk)
> +{
> + struct mem_size_stats *mss = walk->private;
> + struct vm_area_struct *vma = mss->vma;
> + pte_t *pte;
> + spinlock_t *ptl;
>
> - if (PageAnon(page))
> - mss->anonymous += PAGE_SIZE;
> + split_huge_page_pmd(walk->mm, pmd);
>
> - mss->resident += PAGE_SIZE;
> - /* Accumulate the size in pages that have been accessed. */
> - if (pte_young(ptent) || PageReferenced(page))
> - mss->referenced += PAGE_SIZE;
> - mapcount = page_mapcount(page);
> - if (mapcount >= 2) {
> - if (pte_dirty(ptent) || PageDirty(page))
> - mss->shared_dirty += PAGE_SIZE;
> - else
> - mss->shared_clean += PAGE_SIZE;
> - mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
> - } else {
> - if (pte_dirty(ptent) || PageDirty(page))
> - mss->private_dirty += PAGE_SIZE;
> - else
> - mss->private_clean += PAGE_SIZE;
> - mss->pss += (PAGE_SIZE << PSS_SHIFT);
> - }
> - }
> + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> + for (; addr != end; pte++, addr += PAGE_SIZE)
> + smaps_pte_entry(*pte, addr, walk);
> pte_unmap_unlock(pte - 1, ptl);
> cond_resched();
> return 0;
> diff -puN mm/huge_memory.c~break-out-smaps_pte_entry mm/huge_memory.c
> _

Is there a missing change to mm/huge_memory.c?


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