Re: [PATCH v5 0/5] Add movablecore_map boot option

["H. Peter Anvin" <hpa@zytor.com>]

On 01/16/2013 09:08 PM, Yasuaki Ishimatsu wrote:
>
> I thought about the method of specifying the node. But I think
> this method is inconvenience. Node number is decided by OS.
> So the number is changed easily.
>
> for example:
>
> o exmaple 1
>    System has 3 nodes:
>    node0, node1, node2
>
>    When user remove node1, the system has:
>    node0, node2
>
>    But after rebooting the system, the system has:
>    node0, node1
>
>    So node2 becomes node1.
>
> o example 2:
>    System has 2 nodes:
>    0x40000000 - 0x7fffffff : node0
>    0xc0000000 - 0xffffffff : node1
>
>    When user add a node wchih memory range is [0x80000000 - 0xbfffffff],
>    system has:
>    0x40000000 - 0x7fffffff : node0
>    0xc0000000 - 0xffffffff : node1
>    0x80000000 - 0xbfffffff : node2
>
>    But after rebooting the system, the system's node may become:
>    0x40000000 - 0x7fffffff : node0
>    0x80000000 - 0xbfffffff : node1
>    0xc0000000 - 0xffffffff : node2
>
>    So node nunber is changed.
>
> Specifying node number may be easy method than specifying memory
> range. But if user uses node number for specifying removable memory,
> user always need to care whether node number is changed or not at
> every hotplug operation.
>


Well, there are only two options:

1. The user doesn't care which nodes are movable.  In that case, the 
user may just want to specify a target as a percentage of memory to make 
movable -- effectively a "slider" on the performance vs. reliability 
spectrum.  The kernel can then assign nodes arbitrarily.

2. If the user *does* care which nodes are movable, then the user needs 
to be able to specify that *in a way that makes sense to the user*. 
This may mean involving the DMI information as well as SRAT in order to 
get "silk screen" type information out.

	-hpa



-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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