linux-kernel - Re: [PATCH 04/14] mm, memory_hotplug: get rid of is_zone_device

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Date:   Wed, 14 Jun 2017 14:17:31 +0800
From:   Wei Yang <richard.weiyang@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Wei Yang <richard.weiyang@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>, Mel Gorman <mgorman@...e.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH 04/14] mm, memory_hotplug: get rid of
 is_zone_device_section

On Mon, Jun 12, 2017 at 08:49:53AM +0200, Michal Hocko wrote:
>On Sat 10-06-17 22:58:21, Wei Yang wrote:
>> On Sat, Jun 10, 2017 at 5:56 PM, Wei Yang <richard.weiyang@...il.com> wrote:
>[...]
>> > Hmm... one question about the memory_block behavior.
>> >
>> > In case one memory_block contains more than one memory section.
>> > If one section is "device zone", the whole memory_block is not visible
>> > in sysfs. Or until the whole memory_block is full, the sysfs is visible.
>> >
>> 
>> Ok, I made a mistake here. The memory_block device is visible in this
>> case, while the sysfs link between memory_block and node is not visible
>> for the whole memory_block device.
>
>yes the behavior is quite messy
>
>> 
>> BTW, current register_mem_sect_under_node() will create the sysfs
>> link between memory_block and node for each pfn, while actually
>> we only need one link between them. If I am correct.
>> 
>> If you think it is fine, I would like to change this one to create the link
>> on section base.
>
>My longer term plan was to unify all the code to be either memory block
>or memory section oriented. The first sounds more logical from the user
>visible granularity point of view but there might be some corner cases

This means the granularity of hotplug is memory_block instead of mem_section?

While I see the alignment check of add_memory_resource() is SECTION size.

>which would require to use section based approach. I didn't have time to
>study that. If you want to play with that, feel free of course.

Yep, I am really want to help, while these inter-connected concepts makes me
confused. I need to learn more on these.

>-- 
>Michal Hocko
>SUSE Labs

-- 
Wei Yang
Help you, Help me

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