From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 1677960021B for ; Sun, 27 Dec 2009 21:55:14 -0500 (EST) Received: by gxk24 with SMTP id 24so9144043gxk.6 for ; Sun, 27 Dec 2009 18:55:13 -0800 (PST) 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. Message-Id: <20091228115315.76b1ecd0.minchan.kim@barrios-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: lkml , linux-mm , Hugh Dickins , Rik van Riel , KOSAKI Motohiro List-ID: 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 --- 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org