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-wpp7xYTpcfiEpHEz7-oSoVZzRZk22o6 On Wed, Mar 11, 2026 at 09:25:55AM +0100, Vlastimil Babka (SUSE) wrote: > The pointer to barn currently exists in struct kmem_cache_node. That > struct is instantiated for every NUMA node with memory, but we want to > have a barn for every online node (including memoryless). > > Thus decouple the two structures. In struct kmem_cache we have an array > for kmem_cache_node pointers that appears to be sized MAX_NUMNODES but > the actual size calculation in kmem_cache_init() uses nr_node_ids. > Therefore we can't just add another array of barn pointers. Instead > change the array to newly introduced struct kmem_cache_per_node_ptrs > holding both kmem_cache_node and barn pointer. > > Adjust barn accessor and allocation/initialization code accordingly. For > now no functional change intended, barns are created 1:1 together with > kmem_cache_nodes. > > Signed-off-by: Vlastimil Babka (SUSE) > --- > mm/slab.h | 7 +++- > mm/slub.c | 128 +++++++++++++++++++++++++++++++++++--------------------------- > 2 files changed, 78 insertions(+), 57 deletions(-) > > diff --git a/mm/slab.h b/mm/slab.h > index e9ab292acd22..c735e6b4dddb 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -247,7 +252,7 @@ struct kmem_cache { > struct kmem_cache_stats __percpu *cpu_stats; > #endif > > - struct kmem_cache_node *node[MAX_NUMNODES]; > + struct kmem_cache_per_node_ptrs per_node[MAX_NUMNODES]; > }; We should probably turn this into a true flexible array at some point, but that's out of scope for this patchset. > diff --git a/mm/slub.c b/mm/slub.c > index 20cb4f3b636d..609a183f8533 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -436,26 +436,24 @@ struct kmem_cache_node { > /* > - * Get the barn of the current cpu's closest memory node. It may not exist on > - * systems with memoryless nodes but without CONFIG_HAVE_MEMORYLESS_NODES > + * Get the barn of the current cpu's memory node. It may be a memoryless node. > */ > static inline struct node_barn *get_barn(struct kmem_cache *s) > { > - struct kmem_cache_node *n = get_node(s, numa_mem_id()); > - > - if (!n) > - return NULL; > - > - return n->barn; > + return get_barn_node(s, numa_node_id()); > } Previously, memoryless nodes on architectures w/ CONFIG_HAVE_MEMORYLESS_NODES shared the barn of the nearest NUMA node with memory. But now memoryless nodes will have their own barns (after patch 2) regardless of CONFIG_HAVE_MEMORYLESS_NODES, and that's intentional, right? Otherwise LGTM! -- Cheers, Harry / Hyeonggon