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Date: Mon, 28 Dec 2009 11:57:27 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Minchan Kim <minchan.kim@...il.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, lkml <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, Hugh Dickins <hugh.dickins@...cali.co.uk>, Rik van Riel <riel@...hat.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> Subject: Re: [PATCH -mmotm-2009-12-10-17-19] Prevent churning of zero page in LRU list. On Mon, 28 Dec 2009 11:53:15 +0900 Minchan Kim <minchan.kim@...il.com> wrote: > > 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@...il.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.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 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@...ck.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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