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

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Message-ID: <20170614092438.GM6045@dhcp22.suse.cz>
Date:   Wed, 14 Jun 2017 11:24:38 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     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 Wed 14-06-17 17:12:06, Wei Yang wrote:
> On Wed, Jun 14, 2017 at 08:32:06AM +0200, Michal Hocko wrote:
> >On Wed 14-06-17 14:12:59, Wei Yang wrote:
> >[...]
> >> Hi, Michal
> >> 
> >> Not sure you missed this one or you think this is fine.
> >> 
> >> Hmm... this will not happen since we must offline a whole memory_block?
> >
> >yes
> >
> >> So the memory_hotplug/unplug unit is memory_block instead of mem_section?
> >
> >yes.
> 
> If this is true, the check_hotplug_memory_range() should be fixed too.

as I've said earlier. There are many code paths which are quite
confusing and they expect sub-section granularity while they in fact
won't work with sub memblock granularity. This is a larger project
I am afraid and it would be great if you are willing to try to
consolidate that code. I have that on my todo list but there are more
pressing things to address first for me now.

-- 
Michal Hocko
SUSE Labs