On Thu, Feb 03, 2022 at 12:21:16AM +0000, Wei Yang wrote: > 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. I shuffled the words a bit, maybe this sounds better not only to me :) /* * We do not want to confuse userspace by sysfs files/directories for node * without any memory attached to it, so this node is not marked as * N_MEMORY and not marked online so that topology_init() won't create * sysfs hierarchy for this node. The pgdat will get fully initialized by * hotadd_init_pgdat() when memory is hotpluged into this node */ -- Sincerely yours, Mike.
