lkml.org 
[lkml]   [2011]   [Dec]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] pagemap: avoid splitting thp when reading /proc/pid/pagemap
(12/21/11 5:23 PM), Naoya Horiguchi wrote:
> Thp split is not necessary if we explicitly check whether pmds are
> mapping thps or not. This patch introduces the check and the code
> to generate pagemap entries for pmds mapping thps, which results in
> less performance impact of pagemap on thp.
>
> Signed-off-by: Naoya Horiguchi<n-horiguchi@ah.jp.nec.com>
> Reviewed-by: Andi Kleen<ak@linux.intel.com>
>
> Changes since v1:
> - move pfn declaration to the beginning of pagemap_pte_range()
> ---
> fs/proc/task_mmu.c | 49 +++++++++++++++++++++++++++++++++++++++++++------
> 1 files changed, 43 insertions(+), 6 deletions(-)
>
> diff --git 3.2-rc5.orig/fs/proc/task_mmu.c 3.2-rc5/fs/proc/task_mmu.c
> index e418c5a..0df61ab 100644
> --- 3.2-rc5.orig/fs/proc/task_mmu.c
> +++ 3.2-rc5/fs/proc/task_mmu.c
> @@ -600,6 +600,9 @@ struct pagemapread {
> u64 *buffer;
> };
>
> +#define PAGEMAP_WALK_SIZE (PMD_SIZE)
> +#define PAGEMAP_WALK_MASK (PMD_MASK)
> +
> #define PM_ENTRY_BYTES sizeof(u64)
> #define PM_STATUS_BITS 3
> #define PM_STATUS_OFFSET (64 - PM_STATUS_BITS)
> @@ -658,6 +661,22 @@ static u64 pte_to_pagemap_entry(pte_t pte)
> return pme;
> }
>
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +static u64 thp_pte_to_pagemap_entry(pte_t pte, int offset)
> +{
> + u64 pme = 0;
> + if (pte_present(pte))

When does pte_present() return 0?

> + pme = PM_PFRAME(pte_pfn(pte) + offset)
> + | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
> + return pme;
> +}
> +#else
> +static inline u64 thp_pte_to_pagemap_entry(pte_t pte, int offset)
> +{
> + return 0;
> +}
> +#endif
> +
> static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> struct mm_walk *walk)
> {
> @@ -665,14 +684,34 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> struct pagemapread *pm = walk->private;
> pte_t *pte;
> int err = 0;
> -
> - split_huge_page_pmd(walk->mm, pmd);
> + u64 pfn = PM_NOT_PRESENT;
>
> /* find the first VMA at or above 'addr' */
> vma = find_vma(walk->mm, addr);
> - for (; addr != end; addr += PAGE_SIZE) {
> - u64 pfn = PM_NOT_PRESENT;
>
> + spin_lock(&walk->mm->page_table_lock);
> + if (pmd_trans_huge(*pmd)) {
> + if (pmd_trans_splitting(*pmd)) {
> + spin_unlock(&walk->mm->page_table_lock);
> + wait_split_huge_page(vma->anon_vma, pmd);
> + } else {
> + for (; addr != end; addr += PAGE_SIZE) {
> + int offset = (addr& ~PAGEMAP_WALK_MASK)
> + >> PAGE_SHIFT;

implicit narrowing conversion. offset should be unsigned long.


> + pfn = thp_pte_to_pagemap_entry(*(pte_t *)pmd,
> + offset);

This (pte_t*) cast looks introduce new implicit assumption. Please don't
put x86 assumption here directly.




> + err = add_to_pagemap(addr, pfn, pm);
> + if (err)
> + break;
> + }
> + spin_unlock(&walk->mm->page_table_lock);
> + return err;
> + }
> + } else {
> + spin_unlock(&walk->mm->page_table_lock);
> + }

coding standard violation. plz run check_patch.pl.




\
 
 \ /
  Last update: 2011-12-30 04:41    [from the cache]
©2003-2011 Jasper Spaans