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

[Xishi Qiu]

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@xxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Tang Chen <tangchen@xxxxxxxxxxxxxx>
> Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Cc: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
> Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> - 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@xxxxxxxxxx
liuchangsheng@xxxxxxxxxx

Hi Vitaly,

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

Thanks,
Xishi Qiu

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