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Date: Fri, 26 Jun 2015 19:25:03 +0800
From: Xishi Qiu <qiuxishi@huawei.com>
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To: Mel Gorman <mgorman@suse.de>
CC: Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>, Johannes Weiner <hannes@cmpxchg.org>,
        <iamjoonsoo.kim@lge.com>, David Rientjes <rientjes@google.com>,
        <sasha.levin@oracle.com>, Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: fix set pageblock migratetype when boot
References: <558D24C1.5020901@huawei.com> <20150626110424.GI26927@suse.de>
In-Reply-To: <20150626110424.GI26927@suse.de>
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On 2015/6/26 19:04, Mel Gorman wrote:

> On Fri, Jun 26, 2015 at 06:09:05PM +0800, Xishi Qiu wrote:
>> memmap_init_zone()
>> 	...
>> 	if ((z->zone_start_pfn <= pfn)
>> 	    && (pfn < zone_end_pfn(z))
>> 	    && !(pfn & (pageblock_nr_pages - 1)))
>> 		set_pageblock_migratetype(page, MIGRATE_MOVABLE);
>> 	...
>>
>> If the pfn does not align to pageblock, it will not init the migratetype.
> 
> What important impact does that have? It should leave a partial pageblock
> as MIGRATE_UNMOVABLE which is fine by me.
> 

Hi Mel,

The impact is less, it's OK to ignore it.

Thanks,
Xishi Qiu

>> So call it for every page, it will takes more time, but it doesn't matter, 
>> this function will be called only in boot or hotadd memory.
>>
> 
> It's a lot of additional overhead to add to memory initialisation. It
> would need to be for an excellent reason with no alternative solution.
>