Re: [PATCH part4 4/4] x86, acpi, numa, mem_hotplug: Find hotpluggable memory in SRAT memory affinities.

[Tang Chen <tangchen@cn.fujitsu.com>]

On 08/09/2013 12:41 AM, Yinghai Lu wrote:
> On Thu, Aug 8, 2013 at 2:41 AM, Tang Chen<tangchen@cn.fujitsu.com>  wrote:
>> In ACPI SRAT(System Resource Affinity Table), there is a memory affinity for each
>> memory range in the system. In each memory affinity, there is a field indicating
>> that if the memory range is hotpluggable.
>>
>> This patch parses all the memory affinities in SRAT only, and find out all the
>> hotpluggable memory ranges in the system.
>
> oh, no.
>
> How do you make sure the SRAT's entries are right ?
> later numa_init could reject srat table if srat ranges does not cover
> e820 memmap.

In numa_meminfo_cover_memory(), it checks if SRAT covers the e820 ranges.
And it uses
     e820ram = max_pfn - absent_pages_in_range(0, max_pfn)
to calculate the e820 ram size.

Since max_pfn is initialized before memblock.memory is fulfilled, I think
we can also do this check at earlier time.

>
> Also parse srat table two times looks silly.

By parsing SRAT twice, I can avoid memory allocation for acpi_tables_addr
in acpi_initrd_override_copy() procedure at such an early time. This memory
could also be in hotpluggable area.

I think, parsing SRAT memory affinities one more time is clean, no memory
allocation, no global variable initialization. All the current numa init
pathes will work as before.

Thanks.

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