Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752641AbaJ0KeQ (ORCPT ); Mon, 27 Oct 2014 06:34:16 -0400 Received: from cantor2.suse.de ([195.135.220.15]:49353 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751573AbaJ0KeO (ORCPT ); Mon, 27 Oct 2014 06:34:14 -0400 Message-ID: <544E1FA3.4000505@suse.cz> Date: Mon, 27 Oct 2014 11:34:11 +0100 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 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 , Heesub Shin , "Aneesh Kumar K.V" , Ritesh Harjani , t.stanislaws@samsung.com, Gioh Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v4 2/4] mm/page_alloc: add freepage on isolate pageblock to correct buddy list References: <1414051821-12769-1-git-send-email-iamjoonsoo.kim@lge.com> <1414051821-12769-3-git-send-email-iamjoonsoo.kim@lge.com> In-Reply-To: <1414051821-12769-3-git-send-email-iamjoonsoo.kim@lge.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/23/2014 10:10 AM, 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. > > Cc: > Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka > --- > 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 4a5d8e5..5d2f807 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))) { > + 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/