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From: Oscar Salvador <osalvador@suse.de>
To: Michal Hocko <mhocko@kernel.org>
Cc: David Hildenbrand <david@redhat.com>,
	akpm@linux-foundation.org, dan.j.williams@intel.com,
	Jonathan.Cameron@huawei.com, anshuman.khandual@arm.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory
Date: Wed, 3 Apr 2019 10:01:16 +0200	[thread overview]
Message-ID: <20190403080113.adj2m3szhhnvzu56@d104.suse.de> (raw)
In-Reply-To: <20190402124845.GD28293@dhcp22.suse.cz>

On Tue, Apr 02, 2019 at 02:48:45PM +0200, Michal Hocko wrote:
> So what is going to happen when you hotadd two memblocks. The first one
> holds memmaps and then you want to hotremove (not just offline) it?

If you hot-add two memblocks, this means that either:

a) you hot-add a 256MB-memory-device (128MB per memblock)
b) you hot-add two 128MB-memory-device

Either way, hot-removing only works for memory-device as a whole, so
there is no problem.

Vmemmaps are created per hot-added operations, this means that
vmemmaps will be created for the hot-added range.
And since hot-add/hot-remove operations works with the same granularity,
there is no problem.

E.g:

# (qemu) object_add memory-backend-ram,id=ram0,size=128M
# (qemu) device_add pc-dimm,id=dimm0,memdev=ram0,node=1

# (qemu) object_add memory-backend-ram,id=ram1,size=512M
# (qemu) device_add pc-dimm,id=dimm1,memdev=ram1,node=1

# (qemu) object_add memory-backend-ram,id=ram2,size=1G
# (qemu) device_add pc-dimm,id=dimm2,memdev=ram2,node=1

These are three hot-add operations.
Each hot-add operation will create use vmemmaps to hold the memmap for
its hot-added sections.

-- 
Oscar Salvador
SUSE L3

  reply	other threads:[~2019-04-03  8:01 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-28 13:43 [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory Oscar Salvador
2019-03-28 13:43 ` [PATCH 1/4] mm, memory_hotplug: cleanup memory offline path Oscar Salvador
2019-04-03  8:43   ` Michal Hocko
2019-03-28 13:43 ` [PATCH 2/4] mm, memory_hotplug: provide a more generic restrictions for memory hotplug Oscar Salvador
2019-04-03  8:46   ` Michal Hocko
2019-04-03  8:48     ` David Hildenbrand
2019-04-04 10:04     ` Oscar Salvador
2019-04-04 10:06       ` David Hildenbrand
2019-04-04 10:31       ` Michal Hocko
2019-04-04 12:04         ` Oscar Salvador
2019-03-28 13:43 ` [PATCH 3/4] mm, memory_hotplug: allocate memmap from the added memory range for sparse-vmemmap Oscar Salvador
2019-03-28 13:43 ` [PATCH 4/4] mm, sparse: rename kmalloc_section_memmap, __kfree_section_memmap Oscar Salvador
2019-03-28 15:09 ` [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory David Hildenbrand
2019-03-28 15:31   ` David Hildenbrand
2019-03-29  8:45     ` Oscar Salvador
2019-03-29  8:56       ` David Hildenbrand
2019-03-29  9:01         ` David Hildenbrand
2019-03-29  9:20         ` Oscar Salvador
2019-03-29 13:42       ` Michal Hocko
2019-04-01  7:59         ` Oscar Salvador
2019-04-01 11:53           ` Michal Hocko
2019-04-02  8:28             ` Oscar Salvador
2019-04-02  8:39               ` David Hildenbrand
2019-04-02 12:48               ` Michal Hocko
2019-04-03  8:01                 ` Oscar Salvador [this message]
2019-04-03  8:12                   ` Michal Hocko
2019-04-03  8:17                     ` David Hildenbrand
2019-04-03  8:37                       ` Michal Hocko
2019-04-03  8:41                         ` David Hildenbrand
2019-04-03  8:49                           ` Michal Hocko
2019-04-03  8:53                             ` David Hildenbrand
2019-04-03  8:50                           ` Oscar Salvador
2019-04-03  8:54                             ` David Hildenbrand
2019-04-03  9:40                         ` Oscar Salvador
2019-04-03 10:46                           ` Michal Hocko
2019-04-04 10:25                           ` Vlastimil Babka
2019-04-03  8:34                     ` Oscar Salvador
2019-04-03  8:36                       ` David Hildenbrand
2019-03-29  8:30   ` Oscar Salvador
2019-03-29  8:51     ` David Hildenbrand
2019-03-29 22:23 ` John Hubbard
2019-04-01  7:52   ` Oscar Salvador

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