linux-kernel - [PATCH v4 0/2] memory-hotplug: add automatic onlining policy for the newly added memory

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Date:	Tue, 12 Jan 2016 17:56:15 +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 v4 0/2] memory-hotplug: add automatic onlining policy for the newly added memory

Changes since v3:
- Add support for the policy to Xen balloon driver [Daniel Kiper, David Vrabel]
- I found an issue with PATCH v3: when memory auto onlining was requested we
  do nothing to memblocks states so in sysfs they stay 'offline' (while in
  reality they're online). Modify register_new_memory() (and its only caller,
  __add_section()) to create memblocks in the proper state.

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 | 19 +++++++++++++++----
 drivers/base/memory.c            | 40 ++++++++++++++++++++++++++++++++++++----
 drivers/xen/Kconfig              | 20 +++++++++++++-------
 drivers/xen/balloon.c            | 30 +++++++++++++++++++-----------
 include/linux/memory.h           |  3 ++-
 include/linux/memory_hotplug.h   |  4 +++-
 mm/memory_hotplug.c              | 18 +++++++++++++++---
 7 files changed, 103 insertions(+), 31 deletions(-)

-- 
2.5.0