From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx157.postini.com [74.125.245.157]) by kanga.kvack.org (Postfix) with SMTP id 5DF376B006C for ; Thu, 6 Sep 2012 12:34:53 -0400 (EDT) Received: from epcpsbgm2.samsung.com (epcpsbgm2 [203.254.230.27]) by mailout4.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0M9X00KSBSQ3N030@mailout4.samsung.com> for linux-mm@kvack.org; Fri, 07 Sep 2012 01:34:51 +0900 (KST) Received: from amdc1032.localnet ([106.116.147.136]) by mmp2.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTPA id <0M9X001LCSQ1H730@mmp2.samsung.com> for linux-mm@kvack.org; Fri, 07 Sep 2012 01:34:51 +0900 (KST) From: Bartlomiej Zolnierkiewicz Subject: Re: [RFC v2] memory-hotplug: remove MIGRATE_ISOLATE from free_area->free_list Date: Thu, 06 Sep 2012 18:34:35 +0200 References: <1346900018-14759-1-git-send-email-minchan@kernel.org> In-reply-to: <1346900018-14759-1-git-send-email-minchan@kernel.org> MIME-version: 1.0 Message-id: <201209061834.35473.b.zolnierkie@samsung.com> Content-type: Text/Plain; charset=us-ascii Content-transfer-encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Kamezawa Hiroyuki , Yasuaki Ishimatsu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Michal Nazarewicz , Mel Gorman , Wen Congyang , Konrad Rzeszutek Wilk Hi, On Thursday 06 September 2012 04:53:38 Minchan Kim wrote: > Normally, MIGRATE_ISOLATE type is used for memory-hotplug. > But it's irony type because the pages isolated would exist > as free page in free_area->free_list[MIGRATE_ISOLATE] so people > can think of it as allocatable pages but it is *never* allocatable. > It ends up confusing NR_FREE_PAGES vmstat so it would be > totally not accurate so some of place which depend on such vmstat > could reach wrong decision by the context. > > There were already report about it.[1] > [1] 702d1a6e, memory-hotplug: fix kswapd looping forever problem > > Then, there was other report which is other problem.[2] > [2] http://www.spinics.net/lists/linux-mm/msg41251.html > > I believe it can make problems in future, too. > So I hope removing such irony type by another design. > > I hope this patch solves it and let's revert [1] and doesn't need [2]. > > * Changelog v1 > * Fix from Michal's many suggestion > > Cc: Michal Nazarewicz > Cc: Mel Gorman > Cc: Kamezawa Hiroyuki > Cc: Yasuaki Ishimatsu > Cc: Wen Congyang > Cc: Konrad Rzeszutek Wilk > Signed-off-by: Minchan Kim > --- > It's very early version which show the concept so I still marked it with RFC. > I just tested it with simple test and works. > This patch is needed indepth review from memory-hotplug guys from fujitsu > because I saw there are lots of patches recenlty they sent to about > memory-hotplug change. Please take a look at this patch. [...] > @@ -948,8 +954,13 @@ static int move_freepages(struct zone *zone, > } > > order = page_order(page); > - list_move(&page->lru, > - &zone->free_area[order].free_list[migratetype]); > + if (migratetype != MIGRATE_ISOLATE) { > + list_move(&page->lru, > + &zone->free_area[order].free_list[migratetype]); > + } else { > + list_del(&page->lru); > + isolate_free_page(page, order); > + } > page += 1 << order; > pages_moved += 1 << order; > } Shouldn't NR_FREE_PAGES counter be decreased somewhere above? [ I can see that it is not modified in __free_pages_ok() and free_hot_cold_page() because page is still counted as non-free one but here situation is different AFAICS. ] I tested the patch locally here with CONFIG_CMA=y and it causes some major problems for CMA (multiple errors from dma_alloc_from_contiguous() about memory ranges being busy and allocation failures). [ I'm sorry that I don't know more details yet but the issue should be easily reproducible. ] Best regards, -- Bartlomiej Zolnierkiewicz Samsung Poland R&D Center -- 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