linux-kernel - Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions

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Date:   Fri, 7 Jul 2017 16:37:23 +0800
From:   Wei Yang <richard.weiyang@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Wei Yang <richard.weiyang@...il.com>,
        Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        Xishi Qiu <qiuxishi@...wei.com>,
        Kani Toshimitsu <toshi.kani@....com>, slaoub@...il.com,
        Joonsoo Kim <js1304@...il.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions

On Thu, Jul 06, 2017 at 08:56:50AM +0200, Michal Hocko wrote:
>> Below is a result with a little changed kernel to show the start_pfn always.
>> The sequence is:
>> 1. bootup
>> 
>> Node 0, zone  Movable
>>         spanned  65536
>> 	present  0
>> 	managed  0
>>   start_pfn:           0
>> 
>> 2. online movable 2 continuous memory_blocks
>> 
>> Node 0, zone  Movable
>>         spanned  65536
>> 	present  65536
>> 	managed  65536
>>   start_pfn:           1310720
>> 
>> 3. offline 2nd memory_blocks
>> 
>> Node 0, zone  Movable
>>         spanned  65536
>> 	present  32768
>> 	managed  32768
>>   start_pfn:           1310720
>> 
>> 4. offline 1st memory_blocks
>> 
>> Node 0, zone  Movable
>>         spanned  65536
>> 	present  0
>> 	managed  0
>>   start_pfn:           1310720
>> 
>> So I am not sure this is still clearly defined?
>
>Could you be more specific what is not clearly defined? You have
>offlined all online memory blocks so present/managed is 0 while the
>spanned is unchanged because the zone is still defined in range
>[1310720, 1376256].
>

The zone is empty after remove these two memory blocks, while we still think
it is defined in range [1310720, 1376256]. This is what I want to point.

>I also do not see how this is related with the discussed patch as there
>is no zone interleaving involved.

I had a patch which fix the behavior, which means we can make sure the zone is
empty after remove these two memory blocks. As you mentioned in the reply,
http://www.spinics.net/lists/linux-mm/msg130230.html, I thought you would have
this fixed in this cycle. While it looks we will still have this behavior in
this cycle and looks no intend to fix this?

>-- 
>Michal Hocko
>SUSE Labs

-- 
Wei Yang
Help you, Help me

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