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SubjectRe: [PATCH v2 0/5] Add movablecore_map boot option
Hi Tony,

2012/11/29 6:34, Luck, Tony wrote:
>> 1. use firmware information
>> According to ACPI spec 5.0, SRAT table has memory affinity structure
>> and the structure has Hot Pluggable Filed. See "5.2.16.2 Memory
>> Affinity Structure". If we use the information, we might be able to
>> specify movable memory by firmware. For example, if Hot Pluggable
>> Filed is enabled, Linux sets the memory as movable memory.
>>
>> 2. use boot option
>> This is our proposal. New boot option can specify memory range to use
>> as movable memory.
>
> Isn't this just moving the work to the user? To pick good values for the

Yes.

> movable areas, they need to know how the memory lines up across
> node boundaries ... because they need to make sure to allow some
> non-movable memory allocations on each node so that the kernel can
> take advantage of node locality.

There is no problem.
Linux has already two boot options, kernelcore= and movablecore=.
So if we use them, non-movable memory is divided into each node evenly.

But there is no way to specify a node used as movable currently. So
we proposed the new boot option.

> So the user would have to read at least the SRAT table, and perhaps
> more, to figure out what to provide as arguments.
>

> Since this is going to be used on a dynamic system where nodes might
> be added an removed - the right values for these arguments might
> change from one boot to the next. So even if the user gets them right
> on day 1, a month later when a new node has been added, or a broken
> node removed the values would be stale.

I don't think so. Even if we hot add/remove node, the memory range of
each memory device is not changed. So we don't need to change the boot
option.

Thanks,
Yasuaki Ishimatsu

>
> -Tony
>




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