linux-kernel - Re: [PATCH 5/6] mm, memory_hotplug: do not associate hotadded memory to zones until online

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Message-ID: <20170331065002.GD27098@dhcp22.suse.cz>
Date:   Fri, 31 Mar 2017 08:50:02 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Hillf Danton <hillf.zj@...baba-inc.com>
Cc:     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>,
        'Tang Chen' <tangchen@...fujitsu.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@...il.com>,
        'Heiko Carstens' <heiko.carstens@...ibm.com>,
        'Lai Jiangshan' <laijs@...fujitsu.com>,
        'Martin Schwidefsky' <schwidefsky@...ibm.com>
Subject: Re: [PATCH 5/6] mm, memory_hotplug: do not associate hotadded memory
 to zones until online

On Fri 31-03-17 14:18:08, Hillf Danton wrote:
> 
> On March 30, 2017 7:55 PM Michal Hocko wrote:
> > 
> > +static void __meminit resize_zone_range(struct zone *zone, unsigned long start_pfn,
> > +		unsigned long nr_pages)
> > +{
> > +	unsigned long old_end_pfn = zone_end_pfn(zone);
> > +
> > +	if (start_pfn < zone->zone_start_pfn)
> > +		zone->zone_start_pfn = start_pfn;
> > +
> > +	zone->spanned_pages = max(start_pfn + nr_pages, old_end_pfn) - zone->zone_start_pfn;
> > +}
> The implementation above implies zone can only go bigger.

yes, we do not shrink zones currently and I see no poit in doing that
right now.

> Can we resize zone with the given data?

Why couldn't we?

-- 
Michal Hocko
SUSE Labs