From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 8307560021B for ; Sun, 27 Dec 2009 22:00:42 -0500 (EST) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id nBS30efh021644 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 28 Dec 2009 12:00:40 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id F1EA845DE4F for ; Mon, 28 Dec 2009 12:00:39 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id D3C6645DE4D for ; Mon, 28 Dec 2009 12:00:39 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id B7E6E1DB8040 for ; Mon, 28 Dec 2009 12:00:39 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.249.87.106]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 1E50E1DB8044 for ; Mon, 28 Dec 2009 12:00:39 +0900 (JST) Date: Mon, 28 Dec 2009 11:57:27 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH -mmotm-2009-12-10-17-19] Prevent churning of zero page in LRU list. Message-Id: <20091228115727.a1730cdf.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20091228115315.76b1ecd0.minchan.kim@barrios-desktop> References: <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: Minchan Kim Cc: Andrew Morton , lkml , linux-mm , Hugh Dickins , Rik van Riel , KOSAKI Motohiro List-ID: On Mon, 28 Dec 2009 11:53:15 +0900 Minchan Kim 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 Reviewed-by: KAMEZAWA Hiroyuki > --- > 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 > -- 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