Messages in this thread Patch in this message | | | Date | Mon, 28 Dec 2009 11:53:15 +0900 | From | Minchan Kim <> | Subject | [PATCH -mmotm-2009-12-10-17-19] Prevent churning of zero page in LRU list. |
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VM doesn't add zero page to LRU list. It means zero page's churning in LRU list is pointless.
As a matter of fact, zero page can't be promoted by mark_page_accessed since it doesn't have PG_lru.
This patch prevent unecessary mark_page_accessed call of zero page alghouth caller want FOLL_TOUCH.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com> --- mm/memory.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c index 09e4b1b..485f727 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1152,6 +1152,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, spinlock_t *ptl; struct page *page; struct mm_struct *mm = vma->vm_mm; + int zero_pfn = 0; page = follow_huge_addr(mm, address, flags & FOLL_WRITE); if (!IS_ERR(page)) { @@ -1196,15 +1197,15 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, page = vm_normal_page(vma, address, pte); if (unlikely(!page)) { - if ((flags & FOLL_DUMP) || - !is_zero_pfn(pte_pfn(pte))) + zero_pfn = is_zero_pfn(pte_pfn(pte)); + if ((flags & FOLL_DUMP) || !zero_pfn ) goto bad_page; page = pte_page(pte); } if (flags & FOLL_GET) get_page(page); - if (flags & FOLL_TOUCH) { + if (flags & FOLL_TOUCH && !zero_pfn) { if ((flags & FOLL_WRITE) && !pte_dirty(pte) && !PageDirty(page)) set_page_dirty(page); -- 1.5.6.3
-- Kind regards, Minchan Kim
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