Re: [PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes

From: Wei Yang <richard.weiyang@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, Mel Gorman <mgorman@suse.de>,
	Vlastimil Babka <vbabka@suse.cz>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Reza Arbab <arbab@linux.vnet.ibm.com>,
	Yasuaki Ishimatsu <yasu.isimatu@gmail.com>,
	qiuxishi@huawei.com, Kani Toshimitsu <toshi.kani@hpe.com>,
	slaoub@gmail.com, Joonsoo Kim <js1304@gmail.com>,
	Andi Kleen <ak@linux.intel.com>,
	David Rientjes <rientjes@google.com>,
	Daniel Kiper <daniel.kiper@oracle.com>,
	Igor Mammedov <imammedo@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, memory_hotplug: support movable_node for hotplugable nodes
Date: Thu, 15 Jun 2017 11:13:54 +0800	[thread overview]
Message-ID: <20170615031354.GC16833@WeideMacBook-Pro.local> (raw)
In-Reply-To: <20170612064502.GD4145@dhcp22.suse.cz>

[-- Attachment #1: Type: text/plain, Size: 1734 bytes --]

On Mon, Jun 12, 2017 at 08:45:02AM +0200, Michal Hocko wrote:
>On Mon 12-06-17 12:28:32, Wei Yang wrote:
>> On Thu, Jun 08, 2017 at 02:23:18PM +0200, Michal Hocko wrote:
>> >From: Michal Hocko <mhocko@suse.com>
>> >
>> >movable_node kernel parameter allows to make hotplugable NUMA
>> >nodes to put all the hotplugable memory into movable zone which
>> >allows more or less reliable memory hotremove.  At least this
>> >is the case for the NUMA nodes present during the boot (see
>> >find_zone_movable_pfns_for_nodes).
>> >
>> 
>> When movable_node is enabled, we would have overlapped zones, right?
>
>It won't based on this patch. See movable_pfn_range
>

Ok, I went through the code and here maybe a question not that close related
to this patch.

I did some experiment with qemu+kvm and see this.

Guest config: 8G RAM, 2 nodes with 4G on each
Guest kernel: 4.11
Guest kernel command: kernelcore=1G

The log message in kernel is:

[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
[    0.000000]   DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
[    0.000000]   Normal   [mem 0x0000000100000000-0x000000023fffffff]
[    0.000000] Movable zone start for each node
[    0.000000]   Node 0: 0x0000000100000000
[    0.000000]   Node 1: 0x0000000140000000

We see on node 2, ZONE_NORMAL overlap with ZONE_MOVABLE. 
[0x0000000140000000 - 0x000000023fffffff] belongs to both ZONE.

My confusion is:

After we enable ZONE_MOVABLE, no matter whether it is enabled by
"movable_node" or "kernelcore", we would face this kind of overlap? 
Finally, the pages in the overlapped range be belongs to which ZONE?

-- 
Wei Yang
Help you, Help me

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]