From 46156dba32cb68537d36877a97d672227f3e8134 Mon Sep 17 00:00:00 2001 From: Qi Zheng Date: Mon, 10 Nov 2025 16:17:58 +0800 Subject: [PATCH] mm: thp: reparent the split queue during memcg offline Similar to list_lru, the split queue is relatively independent and does not need to be reparented along with objcg and LRU folios (holding objcg lock and lru lock). So let's apply the similar mechanism as list_lru to reparent the split queue separately when memcg is offine. This is also a preparation for reparenting LRU folios. Link: https://lkml.kernel.org/r/8703f907c4d1f7e8a2ef2bfed3036a84fa53028b.1762762324.git.zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Acked-by: Zi Yan Reviewed-by: Muchun Song Acked-by: David Hildenbrand Acked-by: Shakeel Butt Reviewed-by: Harry Yoo Cc: Baolin Wang Cc: Barry Song Cc: Dev Jain Cc: Hugh Dickins Cc: Johannes Weiner Cc: Lance Yang Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Muchun Song Cc: Nico Pache Cc: Roman Gushchin Cc: Ryan Roberts Cc: Wei Yang Signed-off-by: Andrew Morton --- include/linux/huge_mm.h | 4 ++++ include/linux/memcontrol.h | 11 ++++++++++ mm/huge_memory.c | 44 ++++++++++++++++++++++++++++++++++++++ mm/memcontrol.c | 1 + 4 files changed, 60 insertions(+) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 525624c285a63..e2e91aa1a042c 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -415,6 +415,9 @@ static inline int split_huge_page(struct page *page) return split_huge_page_to_list_to_order(page, NULL, 0); } void deferred_split_folio(struct folio *folio, bool partially_mapped); +#ifdef CONFIG_MEMCG +void reparent_deferred_split_queue(struct mem_cgroup *memcg); +#endif void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, unsigned long address, bool freeze); @@ -647,6 +650,7 @@ static inline int try_folio_split_to_order(struct folio *folio, } static inline void deferred_split_folio(struct folio *folio, bool partially_mapped) {} +static inline void reparent_deferred_split_queue(struct mem_cgroup *memcg) {} #define split_huge_pmd(__vma, __pmd, __address) \ do { } while (0) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index b0c6a4635c67b..cc6db20d7dca0 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1775,6 +1775,12 @@ static inline void count_objcg_events(struct obj_cgroup *objcg, bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid); void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg); + +static inline bool memcg_is_dying(struct mem_cgroup *memcg) +{ + return memcg ? css_is_dying(&memcg->css) : false; +} + #else static inline bool mem_cgroup_kmem_disabled(void) { @@ -1845,6 +1851,11 @@ static inline bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid) static inline void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg) { } + +static inline bool memcg_is_dying(struct mem_cgroup *memcg) +{ + return false; +} #endif /* CONFIG_MEMCG */ #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 13684e5376e82..d17d3810a882c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1118,8 +1118,19 @@ static struct deferred_split *split_queue_lock(int nid, struct mem_cgroup *memcg { struct deferred_split *queue; +retry: queue = memcg_split_queue(nid, memcg); spin_lock(&queue->split_queue_lock); + /* + * There is a period between setting memcg to dying and reparenting + * deferred split queue, and during this period the THPs in the deferred + * split queue will be hidden from the shrinker side. + */ + if (unlikely(memcg_is_dying(memcg))) { + spin_unlock(&queue->split_queue_lock); + memcg = parent_mem_cgroup(memcg); + goto retry; + } return queue; } @@ -1129,8 +1140,14 @@ split_queue_lock_irqsave(int nid, struct mem_cgroup *memcg, unsigned long *flags { struct deferred_split *queue; +retry: queue = memcg_split_queue(nid, memcg); spin_lock_irqsave(&queue->split_queue_lock, *flags); + if (unlikely(memcg_is_dying(memcg))) { + spin_unlock_irqrestore(&queue->split_queue_lock, *flags); + memcg = parent_mem_cgroup(memcg); + goto retry; + } return queue; } @@ -4389,6 +4406,33 @@ next: return split; } +#ifdef CONFIG_MEMCG +void reparent_deferred_split_queue(struct mem_cgroup *memcg) +{ + struct mem_cgroup *parent = parent_mem_cgroup(memcg); + struct deferred_split *ds_queue = &memcg->deferred_split_queue; + struct deferred_split *parent_ds_queue = &parent->deferred_split_queue; + int nid; + + spin_lock_irq(&ds_queue->split_queue_lock); + spin_lock_nested(&parent_ds_queue->split_queue_lock, SINGLE_DEPTH_NESTING); + + if (!ds_queue->split_queue_len) + goto unlock; + + list_splice_tail_init(&ds_queue->split_queue, &parent_ds_queue->split_queue); + parent_ds_queue->split_queue_len += ds_queue->split_queue_len; + ds_queue->split_queue_len = 0; + + for_each_node(nid) + set_shrinker_bit(parent, nid, shrinker_id(deferred_split_shrinker)); + +unlock: + spin_unlock(&parent_ds_queue->split_queue_lock); + spin_unlock_irq(&ds_queue->split_queue_lock); +} +#endif + #ifdef CONFIG_DEBUG_FS static void split_huge_pages_all(void) { diff --git a/mm/memcontrol.c b/mm/memcontrol.c index bfc986da3289a..623446821b008 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3920,6 +3920,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) zswap_memcg_offline_cleanup(memcg); memcg_offline_kmem(memcg); + reparent_deferred_split_queue(memcg); reparent_shrinker_deferred(memcg); wb_memcg_offline(memcg); lru_gen_offline_memcg(memcg); -- 2.47.3