From c1b11d76ea9c9ab641afed9ef7df41c31bdde8e1 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Fri, 4 Sep 2026 20:05:22 -0700 Subject: memcg: group the fields of struct mem_cgroup_per_node Replace the two ad-hoc CACHELINE_PADDING members with named cache line groups: memcg_pn_read_mostly memcg, lruvec_stats_percpu, lruvec_stats, shrinker_info, objcg memcg_pn_lruvec lruvec memcg_pn_write_hot lru_zone_size, iter, nmi slab stats memcg_pn_cold orig_objcg, objcg_list The group markers give the same isolation the padding did, but they are named and the build now checks them. lruvec still gets its own lines. Commit f59adcf59332 ("mm: memcg: add cacheline padding after lruvec in mem_cgroup_per_node") showed why that matters: lru_zone_size[] is written under lru_lock but read without it by lruvec_lru_size(), so it must not share a line with lruvec. Splitting the cold fields out costs one extra cache line per node per memcg. No functional change. Link: https://lore.kernel.org/20260905030522.1887837-7-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Signed-off-by: Andrew Morton Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin --- include/linux/memcontrol.h | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) (limited to 'include/linux') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 73594783a2ef..c0c9805b6f03 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -82,7 +82,8 @@ struct mem_cgroup_reclaim_iter { * per-node information in memory controller. */ struct mem_cgroup_per_node { - /* Keep the read-only fields at the start */ + /* Set when the memcg is created, then only read. */ + __cacheline_group_begin_aligned(memcg_pn_read_mostly); struct mem_cgroup *memcg; /* Back pointer, we cannot */ /* use container_of */ @@ -91,14 +92,30 @@ struct mem_cgroup_per_node { struct shrinker_info __rcu *shrinker_info; struct obj_cgroup __rcu *objcg; - CACHELINE_PADDING(_pad1_); + __cacheline_group_end_aligned(memcg_pn_read_mostly); - /* Fields which get updated often at the end. */ + /* + * Keep lruvec on its own lines. Sharing them with lru_zone_size[] + * regressed, see commit f59adcf59332 ("mm: memcg: add cacheline + * padding after lruvec in mem_cgroup_per_node"). + */ + __cacheline_group_begin_aligned(memcg_pn_lruvec); struct lruvec lruvec; - CACHELINE_PADDING(_pad2_); + __cacheline_group_end_aligned(memcg_pn_lruvec); + + /* Written on every LRU update and on every reclaim iteration. */ + __cacheline_group_begin_aligned(memcg_pn_write_hot); long lru_zone_size[MAX_NR_ZONES][NR_LRU_LISTS]; struct mem_cgroup_reclaim_iter iter; +#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC + /* slab stats for nmi context */ + atomic_t slab_reclaimable; + atomic_t slab_unreclaimable; +#endif + __cacheline_group_end_aligned(memcg_pn_write_hot); + /* Touched only when the memcg is reparented or freed. */ + __cacheline_group_begin_aligned(memcg_pn_cold); /* * orig_objcg preserves a pointer (and a reference) to the original * objcg until the end of life of memcg. @@ -106,12 +123,7 @@ struct mem_cgroup_per_node { struct obj_cgroup *orig_objcg; /* list of inherited objcgs, protected by objcg_lock */ struct list_head objcg_list; - -#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC - /* slab stats for nmi context */ - atomic_t slab_reclaimable; - atomic_t slab_unreclaimable; -#endif + __cacheline_group_end_aligned(memcg_pn_cold); }; struct mem_cgroup_threshold { -- cgit v1.2.3