linux-kernel - Re: [PATCH v5 1/2] memory-hotplug: add automatic onlining policy for the newly added memory

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Message-ID: <20160113203444.GY3485@olila.local.net-space.pl>
Date:	Wed, 13 Jan 2016 21:34:44 +0100
From:	Daniel Kiper <daniel.kiper@...cle.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:	linux-mm@...ck.org, Jonathan Corbet <corbet@....net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	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: Re: [PATCH v5 1/2] memory-hotplug: add automatic onlining policy for
 the newly added memory

On Wed, Jan 13, 2016 at 06:32:29PM +0100, 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/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".
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>

Reviewed-by: Daniel Kiper <daniel.kiper@...cle.com>

Daniel