On 03.02.22 10:08, Mike Rapoport wrote: > 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 ;-) I'm usually sending patches against Linus' tree. And I'll post non-RFC most probably today (after testing on aarch64) ;) So I'd appreciate if we could just phrase it more generically, as I tried. But of course, we can try making my life harder ;) -- Thanks, David / dhildenb
