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Date: Wed, 13 Jan 2016 21:34:44 +0100
From: Daniel Kiper <daniel.kiper@oracle.com>
Subject: Re: [PATCH v5 1/2] memory-hotplug: add automatic onlining policy for
 the newly added memory
Message-ID: <20160113203444.GY3485@olila.local.net-space.pl>
References: <1452706350-21158-1-git-send-email-vkuznets@redhat.com>
 <1452706350-21158-2-git-send-email-vkuznets@redhat.com>
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To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: linux-mm@kvack.org, Jonathan Corbet <corbet@lwn.net>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Dan Williams <dan.j.williams@intel.com>, Tang Chen <tangchen@cn.fujitsu.com>, David Vrabel <david.vrabel@citrix.com>, David Rientjes <rientjes@google.com>, Andrew Morton <akpm@linux-foundation.org>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, Xishi Qiu <qiuxishi@huawei.com>, Mel Gorman <mgorman@techsingularity.net>, "K. Y. Srinivasan" <kys@microsoft.com>, Igor Mammedov <imammedo@redhat.com>, Kay Sievers <kay@vrfy.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org

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@redhat.com>

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

Daniel

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