linux-kernel - [PATCH v5 0/2] memory-hotplug: add automatic onlining policy for the newly added memory

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Date:	Wed, 13 Jan 2016 18:32:28 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	linux-mm@...ck.org
Cc:	Jonathan Corbet <corbet@....net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Kiper <daniel.kiper@...cle.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	David Vrabel <david.vrabel@...rix.com>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Xishi Qiu <qiuxishi@...wei.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Kay Sievers <kay@...y.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org
Subject: [PATCH v5 0/2] memory-hotplug: add automatic onlining policy for the newly added memory

Changes since v4:
Patch 1:
- Use memory_block_change_state() through walk_memory_range() instead of
  online_pages() to correctly handle possible failures [David Rientjes]
- Minor memory-hotplug.txt changes (keep the old title, explicitly word
  that we have a global policy here) [David Rientjes, Daniel Kiper]
Patch2:
- 'dom0' -> 'control domain', 'domU' -> 'target domain' in Kconfig
  [David Vrabel]
- always call add_memory_resource() with memhp_auto_online [David Vrabel]

Original description:

Currently, all newly added memory blocks remain in 'offline' state unless
someone onlines them, some linux distributions carry special udev rules
like:

SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online"

to make this happen automatically. This is not a great solution for virtual
machines where memory hotplug is being used to address high memory pressure
situations as such onlining is slow and a userspace process doing this
(udev) has a chance of being killed by the OOM killer as it will probably
require to allocate some memory.

Introduce default policy for the newly added memory blocks in
/sys/devices/system/memory/auto_online_blocks file with two possible
values: "offline" which preserves the current behavior and "online" which
causes all newly added memory blocks to go online as soon as they're added.
The default is "offline".

Vitaly Kuznetsov (2):
  memory-hotplug: add automatic onlining policy for the newly added
    memory
  xen_balloon: support memory auto onlining policy

 Documentation/memory-hotplug.txt | 20 +++++++++++++++++---
 drivers/base/memory.c            | 34 +++++++++++++++++++++++++++++++++-
 drivers/xen/Kconfig              | 20 +++++++++++++-------
 drivers/xen/balloon.c            | 11 ++++++++++-
 include/linux/memory.h           |  3 +++
 include/linux/memory_hotplug.h   |  4 +++-
 mm/memory_hotplug.c              | 17 +++++++++++++++--
 7 files changed, 94 insertions(+), 15 deletions(-)

-- 
2.5.0