On Mon, Jan 25, 2021 at 11:57:20AM +0100, David Hildenbrand wrote: > I'm confused. > > 1. Assume we hotplug memory, online it to ZONE_MOVABLE. The vmemmap gets > allocated from altmap space. The vmemmap could have never been allocated from altmap in case hpage vmemmap feature is enabled. Have a look at [1]. If is_hugetlb_free_vmemmap_enabled(), vmemmap_populate() ends up calling vmemmap_populate_basepages(). And since no memory was consumed from altmap, and hence altmap_alloc_block_buf() was never called, vmem_altmap->alloc will be 0, and memory_block->nr_vmemmap_pages will be 0 as well. But on a second though, true is that we will get in trouble if hpage vmemmap feature ever gets to work with vmemmap_populate_hugepages. I will queue that to look in a new future. [1] https://patchwork.kernel.org/project/linux-mm/patch/20210117151053.24600-10-songmuchun@xxxxxxxxxxxxx/ -- Oscar Salvador SUSE L3
