linux-kernel - Re: [PATCH 18/21] x86, numa: Synchronize nid info in memblock.reserve with numa

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Date:	Thu, 25 Jul 2013 12:09:29 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	tglx@...utronix.de, mingo@...e.hu, hpa@...or.com,
	akpm@...ux-foundation.org, trenn@...e.de, yinghai@...nel.org,
	jiang.liu@...wei.com, wency@...fujitsu.com, laijs@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	mgorman@...e.de, minchan@...nel.org, mina86@...a86.com,
	gong.chen@...ux.intel.com, vasilis.liaskovitis@...fitbricks.com,
	lwoodman@...hat.com, riel@...hat.com, jweiner@...hat.com,
	prarit@...hat.com, zhangyanfei@...fujitsu.com,
	yanghy@...fujitsu.com, x86@...nel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH 18/21] x86, numa: Synchronize nid info in memblock.reserve
 with numa_meminfo.

On 07/24/2013 05:25 AM, Tejun Heo wrote:
> On Fri, Jul 19, 2013 at 03:59:31PM +0800, Tang Chen wrote:
>> Vasilis Liaskovitis found that before we parse SRAT and fulfill numa_meminfo,
>> the nids of all the regions in memblock.reserve[] are MAX_NUMNODES. That is
>> because nids have not been mapped at that time.
>>
>> When we arrange ZONE_MOVABLE in each node later, we need nid in memblock. So
>> after we parse SRAT and fulfill nume_meminfo, synchronize the nid info to
>> memblock.reserve[] immediately.
>
> Having a separate sync is rather nasty.  Why not let
> memblock_set_node() and alloc functions set nid on the reserved
> regions?

Node id and pxm are 1-1 mapped. For the current kernel, before SRAT is 
parsed,
we don't know nid. So all allocated regions are reserved by memblock with
nid = MAX_NUMNODES. So for early allocated memory, we cannot use 
memblock_set_node()
and alloc functions to set the nid.

In this patch-set, we parse SRAT twice, the first one is right after 
memblock is ready.
But we didn't setup nid <-> pxm mapping. So we still have this problem.

And as in [patch 14/21], when reserving hotpluggable memory, we use pxm. 
So my
idea was to do a nid sync in numa_init(). After this, memblock will set 
nid when
it allocates memory.

If we want to let memblock_set_node() and alloc functions set nid on the 
reserved
regions, we should setup nid <-> pxm mapping when we parst SRAT for the 
first time.
If you think this is OK, I can try it.

Thanks.
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