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Message-ID: <20170726123040.GO2981@dhcp22.suse.cz>
Date: Wed, 26 Jul 2017 14:30:41 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Heiko Carstens <heiko.carstens@...ibm.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>,
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>,
Daniel Kiper <daniel.kiper@...cle.com>,
Igor Mammedov <imammedo@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Dan Williams <dan.j.williams@...el.com>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
Michael Ellerman <mpe@...erman.id.au>,
Paul Mackerras <paulus@...ba.org>,
Thomas Gleixner <tglx@...utronix.de>,
Gerald Schaefer <gerald.schaefer@...ibm.com>
Subject: Re: [RFC PATCH 3/5] mm, memory_hotplug: allocate memmap from the
added memory range for sparse-vmemmap
On Wed 26-07-17 13:45:39, Heiko Carstens wrote:
[...]
> In general I do like your idea, however if I understand your patches
> correctly we might have an ordering problem on s390: it is not possible to
> access hot-added memory on s390 before it is online (MEM_GOING_ONLINE
> succeeded).
Could you point me to the code please? I cannot seem to find the
notifier which implements that.
> On MEM_GOING_ONLINE we ask the hypervisor to back the potential available
> hot-added memory region with physical pages. Accessing those ranges before
> that will result in an exception.
Can we make the range which backs the memmap range available? E.g from
s390 specific __vmemmap_populate path?
> However with your approach the memory is still allocated when add_memory()
> is being called, correct? That wouldn't be a change to the current
> behaviour; except for the ordering problem outlined above.
Could you be more specific please? I do not change when the memmap is
allocated.
--
Michal Hocko
SUSE Labs
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