From: Shakeel Butt Date: Tue, 6 May 2025 22:55:32 +0000 (-0700) Subject: memcg: completely decouple memcg and obj stocks X-Git-Tag: v6.16-rc1~92^2~50 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c80509ef65e4e48b1a5cf9dbb98a3ee8be1accb3;p=thirdparty%2Fkernel%2Flinux.git memcg: completely decouple memcg and obj stocks Let's completely decouple the memcg and obj per-cpu stocks. This will enable us to make memcg per-cpu stocks to used without disabling irqs. Also it will enable us to make obj stocks nmi safe independently which is required to make kmalloc/slab safe for allocations from nmi context. Link: https://lkml.kernel.org/r/20250506225533.2580386-4-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Acked-by: Vlastimil Babka Cc: Alexei Starovoitov Cc: Eric Dumaze Cc: Jakub Kacinski Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Sebastian Andrzej Siewior Signed-off-by: Andrew Morton --- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 352aaaeaa536d..1f8611e9a8ffd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1778,12 +1778,22 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) * nr_pages in a single cacheline. This may change in future. */ #define NR_MEMCG_STOCK 7 +#define FLUSHING_CACHED_CHARGE 0 struct memcg_stock_pcp { - local_trylock_t memcg_lock; + local_trylock_t lock; uint8_t nr_pages[NR_MEMCG_STOCK]; struct mem_cgroup *cached[NR_MEMCG_STOCK]; - local_trylock_t obj_lock; + struct work_struct work; + unsigned long flags; +}; + +static DEFINE_PER_CPU_ALIGNED(struct memcg_stock_pcp, memcg_stock) = { + .lock = INIT_LOCAL_TRYLOCK(lock), +}; + +struct obj_stock_pcp { + local_trylock_t lock; unsigned int nr_bytes; struct obj_cgroup *cached_objcg; struct pglist_data *cached_pgdat; @@ -1792,16 +1802,16 @@ struct memcg_stock_pcp { struct work_struct work; unsigned long flags; -#define FLUSHING_CACHED_CHARGE 0 }; -static DEFINE_PER_CPU_ALIGNED(struct memcg_stock_pcp, memcg_stock) = { - .memcg_lock = INIT_LOCAL_TRYLOCK(memcg_lock), - .obj_lock = INIT_LOCAL_TRYLOCK(obj_lock), + +static DEFINE_PER_CPU_ALIGNED(struct obj_stock_pcp, obj_stock) = { + .lock = INIT_LOCAL_TRYLOCK(lock), }; + static DEFINE_MUTEX(percpu_charge_mutex); -static void drain_obj_stock(struct memcg_stock_pcp *stock); -static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, +static void drain_obj_stock(struct obj_stock_pcp *stock); +static bool obj_stock_flush_required(struct obj_stock_pcp *stock, struct mem_cgroup *root_memcg); /** @@ -1824,7 +1834,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) int i; if (nr_pages > MEMCG_CHARGE_BATCH || - !local_trylock_irqsave(&memcg_stock.memcg_lock, flags)) + !local_trylock_irqsave(&memcg_stock.lock, flags)) return ret; stock = this_cpu_ptr(&memcg_stock); @@ -1841,7 +1851,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) break; } - local_unlock_irqrestore(&memcg_stock.memcg_lock, flags); + local_unlock_irqrestore(&memcg_stock.lock, flags); return ret; } @@ -1882,7 +1892,7 @@ static void drain_stock_fully(struct memcg_stock_pcp *stock) drain_stock(stock, i); } -static void drain_local_stock(struct work_struct *dummy) +static void drain_local_memcg_stock(struct work_struct *dummy) { struct memcg_stock_pcp *stock; unsigned long flags; @@ -1890,16 +1900,30 @@ static void drain_local_stock(struct work_struct *dummy) if (WARN_ONCE(!in_task(), "drain in non-task context")) return; - local_lock_irqsave(&memcg_stock.obj_lock, flags); - stock = this_cpu_ptr(&memcg_stock); - drain_obj_stock(stock); - local_unlock_irqrestore(&memcg_stock.obj_lock, flags); + local_lock_irqsave(&memcg_stock.lock, flags); - local_lock_irqsave(&memcg_stock.memcg_lock, flags); stock = this_cpu_ptr(&memcg_stock); drain_stock_fully(stock); clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); - local_unlock_irqrestore(&memcg_stock.memcg_lock, flags); + + local_unlock_irqrestore(&memcg_stock.lock, flags); +} + +static void drain_local_obj_stock(struct work_struct *dummy) +{ + struct obj_stock_pcp *stock; + unsigned long flags; + + if (WARN_ONCE(!in_task(), "drain in non-task context")) + return; + + local_lock_irqsave(&obj_stock.lock, flags); + + stock = this_cpu_ptr(&obj_stock); + drain_obj_stock(stock); + clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); + + local_unlock_irqrestore(&obj_stock.lock, flags); } static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) @@ -1922,10 +1946,10 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) VM_WARN_ON_ONCE(mem_cgroup_is_root(memcg)); if (nr_pages > MEMCG_CHARGE_BATCH || - !local_trylock_irqsave(&memcg_stock.memcg_lock, flags)) { + !local_trylock_irqsave(&memcg_stock.lock, flags)) { /* * In case of larger than batch refill or unlikely failure to - * lock the percpu memcg_lock, uncharge memcg directly. + * lock the percpu memcg_stock.lock, uncharge memcg directly. */ memcg_uncharge(memcg, nr_pages); return; @@ -1957,23 +1981,17 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) WRITE_ONCE(stock->nr_pages[i], nr_pages); } - local_unlock_irqrestore(&memcg_stock.memcg_lock, flags); + local_unlock_irqrestore(&memcg_stock.lock, flags); } -static bool is_drain_needed(struct memcg_stock_pcp *stock, - struct mem_cgroup *root_memcg) +static bool is_memcg_drain_needed(struct memcg_stock_pcp *stock, + struct mem_cgroup *root_memcg) { struct mem_cgroup *memcg; bool flush = false; int i; rcu_read_lock(); - - if (obj_stock_flush_required(stock, root_memcg)) { - flush = true; - goto out; - } - for (i = 0; i < NR_MEMCG_STOCK; ++i) { memcg = READ_ONCE(stock->cached[i]); if (!memcg) @@ -1985,7 +2003,6 @@ static bool is_drain_needed(struct memcg_stock_pcp *stock, break; } } -out: rcu_read_unlock(); return flush; } @@ -2010,15 +2027,27 @@ void drain_all_stock(struct mem_cgroup *root_memcg) migrate_disable(); curcpu = smp_processor_id(); for_each_online_cpu(cpu) { - struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu); - bool flush = is_drain_needed(stock, root_memcg); + struct memcg_stock_pcp *memcg_st = &per_cpu(memcg_stock, cpu); + struct obj_stock_pcp *obj_st = &per_cpu(obj_stock, cpu); - if (flush && - !test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) { + if (!test_bit(FLUSHING_CACHED_CHARGE, &memcg_st->flags) && + is_memcg_drain_needed(memcg_st, root_memcg) && + !test_and_set_bit(FLUSHING_CACHED_CHARGE, + &memcg_st->flags)) { if (cpu == curcpu) - drain_local_stock(&stock->work); + drain_local_memcg_stock(&memcg_st->work); else if (!cpu_is_isolated(cpu)) - schedule_work_on(cpu, &stock->work); + schedule_work_on(cpu, &memcg_st->work); + } + + if (!test_bit(FLUSHING_CACHED_CHARGE, &obj_st->flags) && + obj_stock_flush_required(obj_st, root_memcg) && + !test_and_set_bit(FLUSHING_CACHED_CHARGE, + &obj_st->flags)) { + if (cpu == curcpu) + drain_local_obj_stock(&obj_st->work); + else if (!cpu_is_isolated(cpu)) + schedule_work_on(cpu, &obj_st->work); } } migrate_enable(); @@ -2027,18 +2056,18 @@ void drain_all_stock(struct mem_cgroup *root_memcg) static int memcg_hotplug_cpu_dead(unsigned int cpu) { - struct memcg_stock_pcp *stock; + struct obj_stock_pcp *obj_st; unsigned long flags; - stock = &per_cpu(memcg_stock, cpu); + obj_st = &per_cpu(obj_stock, cpu); - /* drain_obj_stock requires obj_lock */ - local_lock_irqsave(&memcg_stock.obj_lock, flags); - drain_obj_stock(stock); - local_unlock_irqrestore(&memcg_stock.obj_lock, flags); + /* drain_obj_stock requires objstock.lock */ + local_lock_irqsave(&obj_stock.lock, flags); + drain_obj_stock(obj_st); + local_unlock_irqrestore(&obj_stock.lock, flags); /* no need for the local lock */ - drain_stock_fully(stock); + drain_stock_fully(&per_cpu(memcg_stock, cpu)); return 0; } @@ -2835,7 +2864,7 @@ void __memcg_kmem_uncharge_page(struct page *page, int order) } static void __account_obj_stock(struct obj_cgroup *objcg, - struct memcg_stock_pcp *stock, int nr, + struct obj_stock_pcp *stock, int nr, struct pglist_data *pgdat, enum node_stat_item idx) { int *bytes; @@ -2886,13 +2915,13 @@ static void __account_obj_stock(struct obj_cgroup *objcg, static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, struct pglist_data *pgdat, enum node_stat_item idx) { - struct memcg_stock_pcp *stock; + struct obj_stock_pcp *stock; unsigned long flags; bool ret = false; - local_lock_irqsave(&memcg_stock.obj_lock, flags); + local_lock_irqsave(&obj_stock.lock, flags); - stock = this_cpu_ptr(&memcg_stock); + stock = this_cpu_ptr(&obj_stock); if (objcg == READ_ONCE(stock->cached_objcg) && stock->nr_bytes >= nr_bytes) { stock->nr_bytes -= nr_bytes; ret = true; @@ -2901,12 +2930,12 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, __account_obj_stock(objcg, stock, nr_bytes, pgdat, idx); } - local_unlock_irqrestore(&memcg_stock.obj_lock, flags); + local_unlock_irqrestore(&obj_stock.lock, flags); return ret; } -static void drain_obj_stock(struct memcg_stock_pcp *stock) +static void drain_obj_stock(struct obj_stock_pcp *stock) { struct obj_cgroup *old = READ_ONCE(stock->cached_objcg); @@ -2967,32 +2996,35 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock) obj_cgroup_put(old); } -static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, +static bool obj_stock_flush_required(struct obj_stock_pcp *stock, struct mem_cgroup *root_memcg) { struct obj_cgroup *objcg = READ_ONCE(stock->cached_objcg); struct mem_cgroup *memcg; + bool flush = false; + rcu_read_lock(); if (objcg) { memcg = obj_cgroup_memcg(objcg); if (memcg && mem_cgroup_is_descendant(memcg, root_memcg)) - return true; + flush = true; } + rcu_read_unlock(); - return false; + return flush; } static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, bool allow_uncharge, int nr_acct, struct pglist_data *pgdat, enum node_stat_item idx) { - struct memcg_stock_pcp *stock; + struct obj_stock_pcp *stock; unsigned long flags; unsigned int nr_pages = 0; - local_lock_irqsave(&memcg_stock.obj_lock, flags); + local_lock_irqsave(&obj_stock.lock, flags); - stock = this_cpu_ptr(&memcg_stock); + stock = this_cpu_ptr(&obj_stock); if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */ drain_obj_stock(stock); obj_cgroup_get(objcg); @@ -3012,7 +3044,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, stock->nr_bytes &= (PAGE_SIZE - 1); } - local_unlock_irqrestore(&memcg_stock.obj_lock, flags); + local_unlock_irqrestore(&obj_stock.lock, flags); if (nr_pages) obj_cgroup_uncharge_pages(objcg, nr_pages); @@ -5077,9 +5109,12 @@ int __init mem_cgroup_init(void) cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL, memcg_hotplug_cpu_dead); - for_each_possible_cpu(cpu) + for_each_possible_cpu(cpu) { INIT_WORK(&per_cpu_ptr(&memcg_stock, cpu)->work, - drain_local_stock); + drain_local_memcg_stock); + INIT_WORK(&per_cpu_ptr(&obj_stock, cpu)->work, + drain_local_obj_stock); + } memcg_size = struct_size_t(struct mem_cgroup, nodeinfo, nr_node_ids); memcg_cachep = kmem_cache_create("mem_cgroup", memcg_size, 0,