On Thu, Feb 03, 2022 at 09:27:16AM +0100, David Hildenbrand wrote: > On 03.02.22 08:23, Mike Rapoport wrote: > > 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 > > */ > > > > Note that the topology_init() part might change soon [1] so maybe we > want to rephrase that to "so that no sysfs hierarchy will be created via > register_one_node() for this node." right away. Heh, this will be your responsibility to update the comment here when you post non-RFC version ;-) > or (because there is also /sys/devices/system/node/online ) > > "so that the node won't be indicated as online to user space, for > example, via register_one_node()." > > [1] https://lkml.kernel.org/r/20220128151540.164759-1-david@xxxxxxxxxx > > -- > Thanks, > > David / dhildenb > -- Sincerely yours, Mike.
