From: Qi Zheng Date: Wed, 15 Oct 2025 06:35:33 +0000 (+0800) Subject: mm: thp: reparent the split queue during memcg offline X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=b2c2c5bf425daa0b1d3c44e4cffeb56f0ad2e92e;p=users%2Fjedix%2Flinux-maple.git 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/645f537dee489faa45e611d303bf482a06f0ece7.1760509767.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: Mariano Pache Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Ryan Roberts Signed-off-by: Andrew Morton --- diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 396d9e3d1d46..7698b3542c4f 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -409,6 +409,9 @@ 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); @@ -613,6 +616,7 @@ 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 0b2d4ec79adf..5ca97fece690 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1801,6 +1801,11 @@ static inline void count_objcg_events(struct obj_cgroup *objcg, bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid); +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) { @@ -1867,6 +1872,11 @@ static inline bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid) { return true; } + +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 920475659def..370ecfd6a182 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1117,8 +1117,19 @@ 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; } @@ -1128,8 +1139,14 @@ 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; } @@ -4399,6 +4416,33 @@ 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 3ae5cbcaed75..75d1715628f7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3888,6 +3888,7 @@ 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);