From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx201.postini.com [74.125.245.201]) by kanga.kvack.org (Postfix) with SMTP id 70D766B006C for ; Wed, 31 Oct 2012 22:54:20 -0400 (EDT) Message-ID: <5091E5B7.80308@cn.fujitsu.com> Date: Thu, 01 Nov 2012 11:00:07 +0800 From: Wen Congyang 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> <50912A85.5090808@gmail.com> In-Reply-To: <50912A85.5090808@gmail.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Jianguo Wu 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 At 10/31/2012 09:41 PM, Jianguo Wu Wrote: > 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 ? Yes, you are right. I have sent a fix patch. Thanks for pointing it out. Wen Congyang > > 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