Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory

[David Hildenbrand]

On 03.04.19 10:50, Oscar Salvador wrote:
> On Wed, Apr 03, 2019 at 10:41:35AM +0200, David Hildenbrand wrote:
>>> That being said it should be the caller of the hotplug code to tell
>>> the vmemmap allocation strategy. For starter, I would only pack vmemmaps
>>> for "regular" kernel zone memory. Movable zones should be more careful.
>>> We can always re-evaluate later when there is a strong demand for huge
>>> pages on movable zones but this is not the case now because those pages
>>> are not really movable in practice.
>>
>> Remains the issue with potential different user trying to remove memory
>> it didn't add in some other granularity. We then really have to identify
>> and isolate that case.
> 
> If we let the caller specify whether it wants vmemmaps per memblock or range,
> I would trust that caller to do the correct thing and specify one thing or
> another depending on what it wants to do in the future.
> 
> So, say a driver adds 512MB memory and it specifies that it wants vmemmaps per
> memblock because later on it will like to hot-remove in chunks of 128MB.
> 

I am talking about the memtrace and ACPI thing. Otherwise I agree, trust
the user iff the user is the same person adding/removing memory.

-- 

Thanks,

David / dhildenb