From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 7D8596B005A for ; Tue, 21 Apr 2009 20:20:26 -0400 (EDT) Received: from mt1.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n3M0Khfc001288 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 22 Apr 2009 09:20:43 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 2B79E45DE50 for ; Wed, 22 Apr 2009 09:20:43 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id E966445DE53 for ; Wed, 22 Apr 2009 09:20:42 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 7E495E08007 for ; Wed, 22 Apr 2009 09:20:42 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 951F71DB8041 for ; Wed, 22 Apr 2009 09:20:41 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 20/25] Do not check for compound pages during the page allocator sanity checks In-Reply-To: <1240266011-11140-21-git-send-email-mel@csn.ul.ie> References: <1240266011-11140-1-git-send-email-mel@csn.ul.ie> <1240266011-11140-21-git-send-email-mel@csn.ul.ie> Message-Id: <20090422091456.626E.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Wed, 22 Apr 2009 09:20:40 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: kosaki.motohiro@jp.fujitsu.com, Linux Memory Management List , Christoph Lameter , Nick Piggin , Linux Kernel Mailing List , Lin Ming , Zhang Yanmin , Peter Zijlstra , Pekka Enberg , Andrew Morton List-ID: > A number of sanity checks are made on each page allocation and free > including that the page count is zero. page_count() checks for > compound pages and checks the count of the head page if true. However, > in these paths, we do not care if the page is compound or not as the > count of each tail page should also be zero. > > This patch makes two changes to the use of page_count() in the free path. It > converts one check of page_count() to a VM_BUG_ON() as the count should > have been unconditionally checked earlier in the free path. It also avoids > checking for compound pages. > > [mel@csn.ul.ie: Wrote changelog] > Signed-off-by: Nick Piggin > Reviewed-by: Christoph Lameter > --- > mm/page_alloc.c | 6 +++--- > 1 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ec01d8f..376d848 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -425,7 +425,7 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, > return 0; > > if (PageBuddy(buddy) && page_order(buddy) == order) { > - BUG_ON(page_count(buddy) != 0); > + VM_BUG_ON(page_count(buddy) != 0); > return 1; > } > return 0; > Looks good. > @@ -501,7 +501,7 @@ static inline int free_pages_check(struct page *page) > { > if (unlikely(page_mapcount(page) | > (page->mapping != NULL) | > - (page_count(page) != 0) | > + (atomic_read(&page->_count) != 0) | > (page->flags & PAGE_FLAGS_CHECK_AT_FREE))) { > bad_page(page); > return 1; > @@ -646,7 +646,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags) > { > if (unlikely(page_mapcount(page) | > (page->mapping != NULL) | > - (page_count(page) != 0) | > + (atomic_read(&page->_count) != 0) | > (page->flags & PAGE_FLAGS_CHECK_AT_PREP))) { > bad_page(page); > return 1; inserting VM_BUG_ON(PageTail(page)) is better? -- 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