On 02.03.20 15:05, Michal Hocko wrote: > On Mon 02-03-20 14:49:34, David Hildenbrand wrote: >> A virtio-mem device wants to allocate memory from the memory region it >> manages in order to unplug it in the hypervisor - similar to >> a balloon driver. Also, it might want to plug previously unplugged >> (allocated) memory and give it back to Linux. alloc_contig_range() / >> free_contig_range() seem to be the perfect interface for this task. >> >> In contrast to existing balloon devices, a virtio-mem device operates >> on bigger chunks (e.g., 4MB) and only on physical memory it manages. It >> tracks which chunks (subblocks) are still plugged, so it can go ahead >> and try to alloc_contig_range()+unplug them on unplug request, or >> plug+free_contig_range() unplugged chunks on plug requests. >> >> A virtio-mem device will use alloc_contig_range() / free_contig_range() >> only on ranges that belong to the same node/zone in at least >> MAX(MAX_ORDER - 1, pageblock_order) order granularity - e.g., 4MB on >> x86-64. The virtio-mem device added that memory, so the memory >> exists and does not contain any holes. virtio-mem will only try to allocate >> on ZONE_NORMAL, never on ZONE_MOVABLE, just like when allocating >> gigantic pages (we don't put unmovable data into the movable zone). > > Same feedback as in pxm_to_node export. No objections to exporting the > symbol but it would be better to squash this function into the patch > which uses it. The changelog is highly virtio-mem specific anyway. > Maybe it is just a dejavu but I feel I have already said that but I do > not remember any details. As I said back then, I am not a friend of squashing core changes into driver changes (and AFAIK separating such is the common practice - well I have never written a driver myself). I doubt it will make review easier or faster (especially when it comes to patch #1). I can squash #4 into #5, #6 into #7, #8 into #9 if it makes your review easier. -- Thanks, David / dhildenb
