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

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

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@xxxxxxxxxx>

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

Daniel

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