From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f42.google.com (mail-wg0-f42.google.com [74.125.82.42]) by kanga.kvack.org (Postfix) with ESMTP id CC7416B006E for ; Tue, 9 Dec 2014 04:24:29 -0500 (EST) Received: by mail-wg0-f42.google.com with SMTP id z12so269632wgg.1 for ; Tue, 09 Dec 2014 01:24:29 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id q4si1850630wiy.17.2014.12.09.01.24.28 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 09 Dec 2014 01:24:28 -0800 (PST) Message-ID: <5486BFCB.4040305@suse.cz> Date: Tue, 09 Dec 2014 10:24:27 +0100 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: [PATCH 2/3] mm: page_isolation: remove unnecessary freepage_migratetype check for unused page References: <000201d01385$25a6c950$70f45bf0$%yang@samsung.com> In-Reply-To: <000201d01385$25a6c950$70f45bf0$%yang@samsung.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Weijie Yang , iamjoonsoo.kim@lge.com Cc: 'Andrew Morton' , mgorman@suse.de, 'Rik van Riel' , 'Johannes Weiner' , 'Minchan Kim' , 'Weijie Yang' , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 12/09/2014 08:51 AM, Weijie Yang wrote: > when we test the pages in a range is free or not, there is a little > chance we encounter some page which is not in buddy but page_count is 0. > That means that page could be in the page-freeing path but not in the > buddy freelist, such as in pcplist This shouldn't happen anymore IMHO. The pageblock is marked as MIGRATE_ISOLATE and then a lru+pcplist drain is performed. Nothing should be left on pcplist - anything newly freed goes directly to free lists. Hm, maybe it could be on lru cache, but that holds a page reference IIRC, so this test won't pass. > or wait for the zone->lock which the > tester is holding. That could maybe happen, but is it worth testing? If yes, please add it in a comment to the code. > Back to the freepage_migratetype, we use it for a cached value for decide > which free-list the page go when freeing page. If the pageblock is isolated > the page will go to free-list[MIGRATE_ISOLATE] even if the cached type is > not MIGRATE_ISOLATE, the commit ad53f92e(fix incorrect isolation behavior > by rechecking migratetype) patch series have ensure this. > > So the freepage_migratetype check for page_count==0 page in > __test_page_isolated_in_pageblock() is meaningless. > This patch removes the unnecessary freepage_migratetype check. > > Signed-off-by: Weijie Yang > --- > mm/page_isolation.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index 6e5174d..f7c9183 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -223,8 +223,7 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, > page = pfn_to_page(pfn); > if (PageBuddy(page)) > pfn += 1 << page_order(page); > - else if (page_count(page) == 0 && > - get_freepage_migratetype(page) == MIGRATE_ISOLATE) > + else if (page_count(page) == 0) > pfn += 1; > else if (skip_hwpoisoned_pages && PageHWPoison(page)) { > /* > -- 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