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

From: Michal Hocko <mhocko@kernel.org>
To: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: linux-mm@kvack.org, "'Andrew Morton'" <akpm@linux-foundation.org>,
	"'Mel Gorman'" <mgorman@suse.de>,
	"'Vlastimil Babka'" <vbabka@suse.cz>,
	"'Andrea Arcangeli'" <aarcange@redhat.com>,
	"'Reza Arbab'" <arbab@linux.vnet.ibm.com>,
	"'Yasuaki Ishimatsu'" <yasu.isimatu@gmail.com>,
	"'Tang Chen'" <tangchen@cn.fujitsu.com>,
	qiuxishi@huawei.com, "'Kani Toshimitsu'" <toshi.kani@hpe.com>,
	slaoub@gmail.com, "'Joonsoo Kim'" <js1304@gmail.com>,
	"'Andi Kleen'" <ak@linux.intel.com>,
	"'David Rientjes'" <rientjes@google.com>,
	"'Daniel Kiper'" <daniel.kiper@oracle.com>,
	"'Igor Mammedov'" <imammedo@redhat.com>,
	"'Vitaly Kuznetsov'" <vkuznets@redhat.com>,
	"'LKML'" <linux-kernel@vger.kernel.org>,
	"'Dan Williams'" <dan.j.williams@gmail.com>,
	"'Heiko Carstens'" <heiko.carstens@de.ibm.com>,
	"'Lai Jiangshan'" <laijs@cn.fujitsu.com>,
	"'Martin Schwidefsky'" <schwidefsky@de.ibm.com>
Subject: Re: [PATCH 5/6] mm, memory_hotplug: do not associate hotadded memory to zones until online
Date: Fri, 31 Mar 2017 08:50:02 +0200	[thread overview]
Message-ID: <20170331065002.GD27098@dhcp22.suse.cz> (raw)
In-Reply-To: <04c901d2a9e6$91968a20$b4c39e60$@alibaba-inc.com>

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