On 12.05.22 14:50, Muchun Song wrote: > 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. I was asking why vmemmap optimization should take precedence. memmap_on_memory makes it more likely to succeed memory hotplug in close-to-OOM situations -- which is IMHO more important than a vmemmap optimization. But anyhow, the proper approach should most probably be to simply not mess with the vmemmap if we stumble over a vmemmap that's special due to memmap_on_memory. I assume that's what you're talking about sending out. -- Thanks, David / dhildenb
