linux-kernel - Re: [PATCH RFC] memory-hotplug: add automatic onlining policy for the newly added memory

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Date:	Wed, 16 Dec 2015 11:19:26 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
CC:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, 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>,
	Gu Zheng <guz.fnst@...fujitsu.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	yanxiaofeng <yanxiaofeng@...pur.com>,
	Changsheng Liu <liuchangsheng@...pur.com>
Subject: Re: [PATCH RFC] memory-hotplug: add automatic onlining policy for
 the newly added memory

On 2015/12/16 2:05, Vitaly Kuznetsov wrote:

> 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/hotplug_autoonline file with two possible
> values: "offline" (the default) which preserves the current behavior and
> "online" which causes all newly added memory blocks to go online as
> soon as they're added.
> 
> Cc: Jonathan Corbet <corbet@....net>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Daniel Kiper <daniel.kiper@...cle.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Tang Chen <tangchen@...fujitsu.com>
> Cc: David Vrabel <david.vrabel@...rix.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Cc: Gu Zheng <guz.fnst@...fujitsu.com>
> Cc: Xishi Qiu <qiuxishi@...wei.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
> - I was able to find previous attempts to fix the issue, e.g.:
>   http://marc.info/?l=linux-kernel&m=137425951924598&w=2
>   http://marc.info/?l=linux-acpi&m=127186488905382
>   but I'm not completely sure why it didn't work out and the solution
>   I suggest is not 'smart enough', thus 'RFC'.

+ CC: 
yanxiaofeng@...pur.com
liuchangsheng@...pur.com

Hi Vitaly,

Why not use udev rule? I think it can online pages automatically.

Thanks,
Xishi Qiu

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