On Tue, Feb 01, 2022 at 10:54:37AM +0100, Michal Hocko wrote: >On Tue 01-02-22 02:41:19, Wei Yang wrote: >> On Thu, Jan 27, 2022 at 03:47:40PM +0100, Michal Hocko wrote: >> [...] >> >> > + /* >> >> > + * not marking this node online because we do not want to >> >> > + * confuse userspace by sysfs files/directories for node >> >> > + * without any memory attached to it (see topology_init) >> >> > + * The pgdat will get fully initialized when a memory is >> >> > + * hotpluged into it by hotadd_init_pgdat >> >> > + */ >> >> Hmm... which following step would mark the node online? On x86, the node is >> onlined in alloc_node_date(). This is not onlined here. > >The comment tries to explain that this happens during the memory >hotplug. Or maybe I have missed your question? > I am not sure for others, while the comment confused me a little. Currently in kernel, there are two situations for node online: * during memory hotplug * during sys-init For memory hotplug, we allocate pgdat and online node. And current hot-add process has already put them in two steps: 1. __try_online_node() 2. node_set_online() So emphasize "not online" node here, confuse me a little. It is a natural thing to not online node until it has memory. But from another point of view, the comment here is reasonable. During sys-init, we online node at the same time when creating pgdat. And even for memory-less node on x86, we online them too. Well, this is all about the comment. I have tried to grab may head but not come up with a better idea. Or maybe this is just my personal feeling, don't bother if no-one else feel like this. >[...] >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me
