mm: switch deferred split shrinker to list_lru

The deferred split queue handles cgroups in a suboptimal fashion. The queue is per-NUMA node or per-cgroup, not the intersection. That means on a cgrouped system, a node-restricted allocation entering reclaim can end up splitting large pages on other nodes: alloc/unmap deferred_split_folio() list_add_tail(memcg->split_queue) set_shrinker_bit(memcg, node, deferred_shrinker_id) for_each_zone_zonelist_nodemask(restricted_nodes) mem_cgroup_iter() shrink_slab(node, memcg) shrink_slab_memcg(node, memcg) if test_shrinker_bit(memcg, node, deferred_shrinker_id) deferred_split_scan() walks memcg->split_queue The shrinker bit adds an imperfect guard rail. As soon as the cgroup has a single large page on the node of interest, all large pages owned by that memcg, including those on other nodes, will be split. list_lru properly sets up per-node, per-cgroup lists. As a bonus, it streamlines a lot of the list operations and reclaim walks. It's used widely by other major shrinkers already. Convert the deferred split queue as well. The list_lru per-memcg heads are instantiated on demand when the first object of interest is allocated for a cgroup, by calling folio_memcg_alloc_deferred(). Add calls to where splittable pages are created: anon faults, swapin faults, khugepaged collapse. These calls create all possible node heads for the cgroup at once, so the migration code (between nodes) doesn't need any special care. [akpm@linux-foundation.org: fix build with CONFIG_TRANSPARENT_HUGEPAGE=n] Link: https://lore.kernel.org/202605281620.lc3rtkBm-lkp@intel.com [hannes@cmpxchg.org: fix cgroup.memory=nokmem handling] Link: https://lore.kernel.org/ah9PGv12mqai84ES@cmpxchg.org Link: https://lore.kernel.org/20260527204757.2544958-10-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reported-by: Mikhail Zaslonko <zaslonko@linux.ibm.com> Tested-by: Mikhail Zaslonko <zaslonko@linux.ibm.com> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org> Acked-by: Usama Arif <usama.arif@linux.dev> Reviewed-by: Kairui Song <kasong@tencent.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Barry Song <baohua@kernel.org> Cc: Dave Chinner <david@fromorbit.com> Cc: David Hildenbrand (Arm) <david@kernel.org> Cc: Dev Jain <dev.jain@arm.com> Cc: Lance Yang <lance.yang@linux.dev> Cc: Liam R. Howlett <liam@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nico Pache <npache@redhat.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: Zi Yan <ziy@nvidia.com> Cc: kernel test robot <lkp@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

JWJohannes Weiner committed 5 months ago