On Tue 07-12-21 16:34:30, David Hildenbrand wrote: > On 07.12.21 16:29, Michal Hocko wrote: > > On Tue 07-12-21 16:09:39, David Hildenbrand wrote: > >> On 07.12.21 14:23, Michal Hocko wrote: > >>> On Tue 07-12-21 13:28:31, David Hildenbrand wrote: > >>> [...] > >>>> But maybe I am missing something important regarding online vs. offline > >>>> nodes that your patch changes? > >>> > >>> I am relying on alloc_node_data setting the node online. But if we are > >>> to change the call to arch_alloc_node_data then the patch needs to be > >>> more involved. Here is what I have right now. If this happens to be the > >>> right way then there is some additional work to sync up with the hotplug > >>> code. > >>> > >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > >>> index c5952749ad40..a296e934ad2f 100644 > >>> --- a/mm/page_alloc.c > >>> +++ b/mm/page_alloc.c > >>> @@ -8032,8 +8032,23 @@ void __init free_area_init(unsigned long *max_zone_pfn) > >>> /* Initialise every node */ > >>> mminit_verify_pageflags_layout(); > >>> setup_nr_node_ids(); > >>> - for_each_online_node(nid) { > >>> - pg_data_t *pgdat = NODE_DATA(nid); > >>> + for_each_node(nid) { > >>> + pg_data_t *pgdat; > >>> + > >>> + if (!node_online(nid)) { > >>> + pr_warn("Node %d uninitialized by the platform. Please report with memory map.\n", nid); > >>> + pgdat = arch_alloc_nodedata(nid); > >>> + pgdat->per_cpu_nodestats = alloc_percpu(struct per_cpu_nodestat); > >>> + arch_refresh_nodedata(nid, pgdat); > >>> + node_set_online(nid); > >> > >> Setting all possible nodes online might result in quite some QE noice, > >> because all these nodes will then be visible in the sysfs and > >> try_offline_nodes() is essentially for the trash. > > > > I am not sure I follow. I believe sysfs will not get populate because I > > do not call register_one_node. > > arch/x86/kernel/topology.c:topology_init() > > for_each_online_node(i) > register_one_node(i); Right you are. > > You are right that try_offline_nodes will be reduce which is good imho. > > More changes will be possible (hopefully to drop some ugly code) on top > > of this change (or any other that achieves that there are no NULL pgdat > > for possible nodes). > > > > No to exposing actually offline nodes to user space via sysfs. Why is that a problem with the sysfs for non-populated nodes? -- Michal Hocko SUSE Labs