From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f176.google.com (mail-wi0-f176.google.com [209.85.212.176]) by kanga.kvack.org (Postfix) with ESMTP id 49F0F6B0038 for ; Thu, 20 Aug 2015 03:42:03 -0400 (EDT) Received: by wicne3 with SMTP id ne3so8012855wic.1 for ; Thu, 20 Aug 2015 00:42:02 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id xb1si6952589wjc.15.2015.08.20.00.42.01 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 20 Aug 2015 00:42:01 -0700 (PDT) Subject: Re: [PATCH V2] mm:memory hot-add: memory can not been added to movable zone References: <1440055685-6083-1-git-send-email-liuchangsheng@inspur.com> From: Vlastimil Babka Message-ID: <55D584C7.7060101@suse.cz> Date: Thu, 20 Aug 2015 09:41:59 +0200 MIME-Version: 1.0 In-Reply-To: <1440055685-6083-1-git-send-email-liuchangsheng@inspur.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Changsheng Liu , akpm@linux-foundation.org, isimatu.yasuaki@jp.fujitsu.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, yanxiaofeng@inspur.com, fandd@inspur.com, Changsheng Liu On 08/20/2015 09:28 AM, Changsheng Liu wrote: > From: Changsheng Liu > > When memory is hot added, should_add_memory_movable() always returns 0 > because the movable zone is empty, so the memory that was hot added will > add to the normal zone even if we want to remove the memory. I'm not expert on memory hot-plug, but since you CC'd me, I wonder... the function has this comment: " * If movable zone has already been setup, newly added memory should be check." So I read it like "if you want movable memory *at all*, you should do some setup first" (but don't ask me what setup). After your patch, every hot-added memory would be automatically movable? Isn't that silently changing behavior against user expectations? What about those that don't want to hot-remove and don't want movable zones (which limit what kind of allocations are possible), is there a way to prevent memory being movable after your patch? > So we change should_add_memory_movable(): if the user config > CONFIG_MOVABLE_NODE it will return 1 when the movable zone is empty. > > Reviewed-by: Andrew Morton > Signed-off-by: Changsheng Liu > Tested-by: Dongdong Fan > --- > mm/memory_hotplug.c | 3 +-- > 1 files changed, 1 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 26fbba7..ff658f2 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1199,8 +1199,7 @@ static int should_add_memory_movable(int nid, u64 start, u64 size) > struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE; > > if (zone_is_empty(movable_zone)) > - return 0; > - > + return IS_ENABLED(CONFIG_MOVABLE_NODE); > if (movable_zone->zone_start_pfn <= start_pfn) > return 1; > > -- 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