Re: [PATCH v2 0/5] Add movablecore_map boot option

[Jiang Liu]

Hi Yasuaki,
	Forgot to mention that I have no objection to this patchset.
I think it's a good start point, but we still need to improve usabilities
of memory hotplug by passing platform specific information from BIOS.
And mechanism provided by this patchset will/may be used to improve
usabilities too. 

Regards!
Gerry

On 11/29/2012 06:38 PM, Yasuaki Ishimatsu wrote:
> 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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