Re: [PATCH v10 2/4] mm: memory_hotplug: override memmap_on_memory when hugetlb_free_vmemmap=on

[Muchun Song]

On Thu, May 12, 2022 at 09:36:15AM +0200, David Hildenbrand wrote:
> On 09.05.22 08:27, Muchun Song wrote:
> > Optimizing HugeTLB vmemmap pages is not compatible with allocating memmap on
> > hot added memory. If "hugetlb_free_vmemmap=on" and
> > memory_hotplug.memmap_on_memory" are both passed on the kernel command line,
> > optimizing hugetlb pages takes precedence. 
> 
> Why?
>

Because both two features are not compatible since hugetlb_free_vmemmap cannot
optimize the vmemmap pages allocated from alternative allocator (when
memory_hotplug.memmap_on_memory=1). So when the feature of hugetlb_free_vmemmap
is introduced, I made hugetlb_free_vmemmap take precedence.  BTW, I have a plan
to remove this restriction, I'll post it out ASAP.

Thanks.