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Date: Tue, 16 Jun 2015 11:46:18 +0200
From: Vlastimil Babka <vbabka@suse.cz>
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To: Xishi Qiu <qiuxishi@huawei.com>
CC: Andrew Morton <akpm@linux-foundation.org>, nao.horiguchi@gmail.com,
        Yinghai Lu <yinghai@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>, mingo@elte.hu,
        Xiexiuqi <xiexiuqi@huawei.com>, Hanjun Guo <guohanjun@huawei.com>,
        "Luck, Tony" <tony.luck@intel.com>, Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 00/12] mm: mirrored memory support for page buddy
 allocations
References: <55704A7E.5030507@huawei.com> <557FD5F8.10903@suse.cz> <557FDB9B.1090105@huawei.com>
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On 06/16/2015 10:17 AM, Xishi Qiu wrote:
> On 2015/6/16 15:53, Vlastimil Babka wrote:
> 
>> On 06/04/2015 02:54 PM, Xishi Qiu wrote:
>>>
>>> I think add a new migratetype is btter and easier than a new zone, so I use
>> 
>> If the mirrored memory is in a single reasonably compact (no large holes) range
>> (per NUMA node) and won't dynamically change its size, then zone might be a
>> better option. For one thing, it will still allow distinguishing movable and
>> unmovable allocations within the mirrored memory.
>> 
>> We had enough fun with MIGRATE_CMA and all kinds of checks it added to allocator
>> hot paths, and even CMA is now considering moving to a separate zone.
>> 
> 
> Hi, how about the problem of this case:
> e.g. node 0: 0-4G(dma and dma32)
>      node 1: 4G-8G(normal), 8-12G(mirror), 12-16G(normal),
> so more than one normal zone in a node? or normal zone just span the mirror zone?

Normal zone can span the mirror zone just fine. However, it will result in zone
scanners such as compaction to skip over the mirror zone inefficiently. Hmm...