From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id 2AA2E82F64 for ; Wed, 4 Nov 2015 22:17:56 -0500 (EST) Received: by pabfh17 with SMTP id fh17so72646693pab.0 for ; Wed, 04 Nov 2015 19:17:55 -0800 (PST) Received: from bgp253.corp-email.cn (bgp253.corp-email.cn. [112.65.243.253]) by mx.google.com with SMTP id rs4si6665373pbb.50.2015.11.04.19.17.52 for ; Wed, 04 Nov 2015 19:17:55 -0800 (PST) Subject: Re: [PATCH V8] mm: memory hot-add: hot-added memory can not be added to movable zone by default References: <1446625415-11941-1-git-send-email-liuchangsheng@inspur.com> <563A32DD.1040903@intel.com> From: Changsheng Liu Message-ID: <563AC8C0.40007@inspur.com> Date: Thu, 5 Nov 2015 11:10:56 +0800 MIME-Version: 1.0 In-Reply-To: <563A32DD.1040903@intel.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen , akpm@linux-foundation.org, isimatu.yasuaki@jp.fujitsu.com, vbabka@suse.cz, yasu.isimatu@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, wunan@inspur.com, yanxiaofeng@inspur.com, fandd@inspur.com, Wang Nan , Yinghai Lu , Tang Chen , Toshi Kani , Xishi Qiu a?? 2015/11/5 0:31, Dave Hansen a??e??: > On 11/04/2015 12:23 AM, liuchangsheng wrote: >> After the user config CONFIG_MOVABLE_NODE, >> When the memory is hot added, should_add_memory_movable() return 0 >> because all zones including ZONE_MOVABLE are empty, >> so the memory that was hot added will be assigned to ZONE_NORMAL, >> and we need using the udev rules to online the memory automatically: >> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", >> ATTR{state}="online_movable" >> The memory block onlined by udev must be adjacent to ZONE_MOVABLE. >> The events of memory section are notified to udev asynchronously, >> so it can not ensure that the memory block onlined by udev is >> adjacent to ZONE_MOVABLE.So it can't ensure memory online always success. >> But we want the whole node to be added to ZONE_MOVABLE by default. > I'm still a bit confused about the whole scenario here. > > Is the core problem: > 1. We add memory in a new node and that node can not be made entirely > movable? As I know, System will not ensure that the node can be made entirely movable if the memory of the node is assigned to ZONE_NORMAL > or > 2. We add memory to an existing zone that has some non-movable memory > and we want the new memory to be movable? It will work if we want to let the memroy movable by using movable_node > >> @@ -1201,6 +1201,9 @@ static int check_hotplug_memory_range(u64 start, u64 size) >> /* >> * If movable zone has already been setup, newly added memory should be check. >> * If its address is higher than movable zone, it should be added as movable. >> + * And if system boots up with movable_node and config CONFIG_MOVABLE_NOD and >> + * added memory does not overlap the zone before MOVABLE_ZONE, >> + * the memory is added as movable. >> * Without this check, movable zone may overlap with other zone. >> */ > This comment is describing what the code does, but is rather sparse on > why. This scenario is pretty convoluted and I can barely make sense of > why it is doing this today while looking at the whole changelog, much > less in a few years when the original changelog will be harder to come by. > > Also please put the comment next to the new if() statement. It's really > hard to match the comment to the code the way you have it now. > >> static int should_add_memory_movable(int nid, u64 start, u64 size) >> @@ -1208,6 +1211,10 @@ static int should_add_memory_movable(int nid, u64 start, u64 size) >> unsigned long start_pfn = start >> PAGE_SHIFT; >> pg_data_t *pgdat = NODE_DATA(nid); >> struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE; >> + struct zone *pre_zone = pgdat->node_zones + (ZONE_MOVABLE - 1); >> + >> + if (movable_node_is_enabled() && (zone_end_pfn(pre_zone) <= start_pfn)) >> + return 1; >> >> if (zone_is_empty(movable_zone)) >> return 0; >> > . > -- 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