From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id 83A5A6B010D for ; Mon, 3 Nov 2014 03:22:16 -0500 (EST) Received: by mail-pa0-f51.google.com with SMTP id kq14so11746312pab.38 for ; Mon, 03 Nov 2014 00:22:16 -0800 (PST) Received: from mailout2.samsung.com (mailout2.samsung.com. [203.254.224.25]) by mx.google.com with ESMTPS id fl13si1035821pdb.111.2014.11.03.00.22.14 for (version=TLSv1 cipher=RC4-MD5 bits=128/128); Mon, 03 Nov 2014 00:22:15 -0800 (PST) Received: from epcpsbgr4.samsung.com (u144.gpu120.samsung.co.kr [203.254.230.144]) by mailout2.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0NEG00K51F90DM20@mailout2.samsung.com> for linux-mm@kvack.org; Mon, 03 Nov 2014 17:22:12 +0900 (KST) Message-id: <54573B3B.4070500@samsung.com> Date: Mon, 03 Nov 2014 17:22:19 +0900 From: Heesub Shin MIME-version: 1.0 Subject: Re: [PATCH v5 2/4] mm/page_alloc: add freepage on isolate pageblock to correct buddy list References: <1414740330-4086-1-git-send-email-iamjoonsoo.kim@lge.com> <1414740330-4086-3-git-send-email-iamjoonsoo.kim@lge.com> In-reply-to: <1414740330-4086-3-git-send-email-iamjoonsoo.kim@lge.com> Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim , Andrew Morton Cc: "Kirill A. Shutemov" , Rik van Riel , Peter Zijlstra , Mel Gorman , Johannes Weiner , Minchan Kim , Yasuaki Ishimatsu , Zhang Yanfei , Tang Chen , Naoya Horiguchi , Bartlomiej Zolnierkiewicz , Wen Congyang , Marek Szyprowski , Michal Nazarewicz , Laura Abbott , "Aneesh Kumar K.V" , Ritesh Harjani , Gioh Kim , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Hello, On 10/31/2014 04:25 PM, Joonsoo Kim wrote: > In free_pcppages_bulk(), we use cached migratetype of freepage > to determine type of buddy list where freepage will be added. > This information is stored when freepage is added to pcp list, so > if isolation of pageblock of this freepage begins after storing, > this cached information could be stale. In other words, it has > original migratetype rather than MIGRATE_ISOLATE. > > There are two problems caused by this stale information. One is that > we can't keep these freepages from being allocated. Although this > pageblock is isolated, freepage will be added to normal buddy list > so that it could be allocated without any restriction. And the other > problem is incorrect freepage accounting. Freepages on isolate pageblock > should not be counted for number of freepage. > > Following is the code snippet in free_pcppages_bulk(). > > /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ > __free_one_page(page, page_to_pfn(page), zone, 0, mt); > trace_mm_page_pcpu_drain(page, 0, mt); > if (likely(!is_migrate_isolate_page(page))) { > __mod_zone_page_state(zone, NR_FREE_PAGES, 1); > if (is_migrate_cma(mt)) > __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1); > } > > As you can see above snippet, current code already handle second problem, > incorrect freepage accounting, by re-fetching pageblock migratetype > through is_migrate_isolate_page(page). But, because this re-fetched > information isn't used for __free_one_page(), first problem would not be > solved. This patch try to solve this situation to re-fetch pageblock > migratetype before __free_one_page() and to use it for __free_one_page(). > > In addition to move up position of this re-fetch, this patch use > optimization technique, re-fetching migratetype only if there is > isolate pageblock. Pageblock isolation is rare event, so we can > avoid re-fetching in common case with this optimization. > > This patch also correct migratetype of the tracepoint output. > > Cc: > Acked-by: Minchan Kim > Acked-by: Michal Nazarewicz > Acked-by: Vlastimil Babka > Signed-off-by: Joonsoo Kim > --- > mm/page_alloc.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index f7a867e..6df23fe 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -725,14 +725,17 @@ static void free_pcppages_bulk(struct zone *zone, int count, > /* must delete as __free_one_page list manipulates */ > list_del(&page->lru); > mt = get_freepage_migratetype(page); > + if (unlikely(has_isolate_pageblock(zone))) { How about adding an additional check for 'mt == MIGRATE_MOVABLE' here? Then, most of get_pageblock_migratetype() calls could be avoided while the isolation is in progress. I am not sure this is the case on memory offlining. How do you think? > + mt = get_pageblock_migratetype(page); > + if (is_migrate_isolate(mt)) > + goto skip_counting; > + } > + __mod_zone_freepage_state(zone, 1, mt); > + > +skip_counting: > /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ > __free_one_page(page, page_to_pfn(page), zone, 0, mt); > trace_mm_page_pcpu_drain(page, 0, mt); > - if (likely(!is_migrate_isolate_page(page))) { > - __mod_zone_page_state(zone, NR_FREE_PAGES, 1); > - if (is_migrate_cma(mt)) > - __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1); > - } > } while (--to_free && --batch_free && !list_empty(list)); > } > spin_unlock(&zone->lock); > -- 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