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[140.211.169.12]) by mx.google.com with ESMTPS id i14si39366pgb.0.2019.04.17.15.03.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 15:03:33 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id E04B4B3E; Wed, 17 Apr 2019 22:03:32 +0000 (UTC) Date: Wed, 17 Apr 2019 15:03:31 -0700 From: Andrew Morton To: Dan Williams Cc: David Hildenbrand , =?ISO-8859-1?Q?J=E9r=F4me?= Glisse , Logan Gunthorpe , Toshi Kani , Jeff Moyer , Michal Hocko , Vlastimil Babka , stable@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 00/12] mm: Sub-section memory hotplug support Message-Id: <20190417150331.90219ca42a1c0db8632d0fd5@linux-foundation.org> In-Reply-To: <155552633539.2015392.2477781120122237934.stgit@dwillia2-desk3.amr.corp.intel.com> References: <155552633539.2015392.2477781120122237934.stgit@dwillia2-desk3.amr.corp.intel.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams wrote: > The memory hotplug section is an arbitrary / convenient unit for memory > hotplug. 'Section-size' units have bled into the user interface > ('memblock' sysfs) and can not be changed without breaking existing > userspace. The section-size constraint, while mostly benign for typical > memory hotplug, has and continues to wreak havoc with 'device-memory' > use cases, persistent memory (pmem) in particular. Recall that pmem uses > devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a > 'struct page' memmap for pmem. However, it does not use the 'bottom > half' of memory hotplug, i.e. never marks pmem pages online and never > exposes the userspace memblock interface for pmem. This leaves an > opening to redress the section-size constraint. v6 and we're not showing any review activity. Who would be suitable people to help out here?