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Date: Tue, 19 Jan 2016 14:44:07 -0800 (PST)
From: David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v6 1/2] memory-hotplug: add automatic onlining policy
 for the newly added memory
In-Reply-To: <1452864645-27778-2-git-send-email-vkuznets@redhat.com>
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References: <1452864645-27778-1-git-send-email-vkuznets@redhat.com> <1452864645-27778-2-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>, Daniel Kiper <daniel.kiper@oracle.com>, Dan Williams <dan.j.williams@intel.com>, Tang Chen <tangchen@cn.fujitsu.com>, David Vrabel <david.vrabel@citrix.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 Fri, 15 Jan 2016, 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".
> 
> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Acked-by: David Rientjes <rientjes@google.com>

Thanks for the very good documentation!

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