Re: [RFC PATCH 0/7] Memory hotplug/hotremove at subsection size

Zi Yan
2021-05-06T15:50:08Z

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On 6 May 2021, at 11:40, David Hildenbrand wrote:

>>>> The last patch increases SECTION_SIZE_BITS to demonstrate the use of memory
>>>> hotplug/hotremove subsection, but is not intended to be merged as is. It is
>>>> there in case one wants to try this out and will be removed during the final
>>>> submission.
>>>>
>>>> Feel free to give suggestions and comments. I am looking forward to your
>>>> feedback.
>>>
>>> Please not like this.
>>
>> Do you mind sharing more useful feedback instead of just saying a lot of No?
>
> I remember reasoning about this already in another thread, no? Either you're ignoring my previous feedback or my mind is messing with me.

I definitely remember all your suggestions:

1. do not use CMA allocation for 1GB THP.
2. section size defines the minimum size in which we can add_memory(), so we cannot increase it.

I am trying an alternative here. I am not using CMA allocation and not increasing the minimum size of add_memory() by decoupling the memory block size from section size, so that add_memory() can add a memory block smaller (as small as 2MB, the subsection size) than section size. In this way, section size can be increased freely. I do not see the strong tie between add_memory() and section size, especially we have subsection bitmap support.

—
Best Regards,
Yan Zi

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