From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx190.postini.com [74.125.245.190]) by kanga.kvack.org (Postfix) with SMTP id 9FB686B006C for ; Wed, 31 Oct 2012 09:41:37 -0400 (EDT) Received: by mail-pb0-f41.google.com with SMTP id rq2so1090727pbb.14 for ; Wed, 31 Oct 2012 06:41:36 -0700 (PDT) Message-ID: <50912A85.5090808@gmail.com> Date: Wed, 31 Oct 2012 21:41:25 +0800 From: Jianguo Wu MIME-Version: 1.0 Subject: Re: [Patch v4 3/8] memory-hotplug: fix NR_FREE_PAGES mismatch References: <1351682594-17347-1-git-send-email-wency@cn.fujitsu.com> <1351682594-17347-4-git-send-email-wency@cn.fujitsu.com> In-Reply-To: <1351682594-17347-4-git-send-email-wency@cn.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Wen Congyang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, Jiang Liu , Len Brown , Andrew Morton , KOSAKI Motohiro , Yasuaki Ishimatsu , rjw@sisk.pl, Lai Jiangshan , David Rientjes , Benjamin Herrenschmidt , Paul Mackerras , Christoph Lameter , Minchan Kim , Dave Hansen , Mel Gorman On 2012/10/31 19:23, Wen Congyang wrote: > NR_FREE_PAGES will be wrong after offlining pages. We add/dec > NR_FREE_PAGES like this now: > > 1. move all pages in buddy system to MIGRATE_ISOLATE, and dec NR_FREE_PAGES > > 2. don't add NR_FREE_PAGES when it is freed and the migratetype is > MIGRATE_ISOLATE > > 3. dec NR_FREE_PAGES when offlining isolated pages. > > 4. add NR_FREE_PAGES when undoing isolate pages. > > When we come to step 3, all pages are in MIGRATE_ISOLATE list, and > NR_FREE_PAGES are right. When we come to step4, all pages are not in > buddy system, so we don't change NR_FREE_PAGES in this step, but we change > NR_FREE_PAGES in step3. So NR_FREE_PAGES is wrong after offlining pages. > So there is no need to change NR_FREE_PAGES in step3. > > This patch also fixs a problem in step2: if the migratetype is > MIGRATE_ISOLATE, we should not add NR_FRR_PAGES when we remove pages from > pcppages. > > Signed-off-by: Wen Congyang > Cc: David Rientjes > Cc: Jiang Liu > Cc: Len Brown > Cc: Benjamin Herrenschmidt > Cc: Paul Mackerras > Cc: Christoph Lameter > Cc: Minchan Kim > Cc: KOSAKI Motohiro > Cc: Yasuaki Ishimatsu > Cc: Dave Hansen > Cc: Mel Gorman > Signed-off-by: Andrew Morton > --- > mm/page_alloc.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5b74de6..a7cd2d1 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -667,11 +667,13 @@ static void free_pcppages_bulk(struct zone *zone, int count, > /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ > __free_one_page(page, zone, 0, mt); > trace_mm_page_pcpu_drain(page, 0, mt); > - if (is_migrate_cma(mt)) > - __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1); > + if (likely(mt != MIGRATE_ISOLATE)) { Hi Congyang, I think mt != MIGRATE_ISOLATE is always true here, page from PCP's migratetype < MIGRATE_PCPTYPES. When isolate page, we change pageblock's migratetype to MIGRATE_ISOLATE, but set_freepage_migratetype() isn't called. Maybe we can use mt = get_pageblock_migratetype() here ? Thanks, Jianguo Wu. > + __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)); > } > - __mod_zone_page_state(zone, NR_FREE_PAGES, count); > spin_unlock(&zone->lock); > } > > @@ -5987,8 +5989,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) > list_del(&page->lru); > rmv_page_order(page); > zone->free_area[order].nr_free--; > - __mod_zone_page_state(zone, NR_FREE_PAGES, > - - (1UL << order)); > for (i = 0; i < (1 << order); i++) > SetPageReserved((page+i)); > pfn += (1 << order); > -- 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