Messages in this thread | | | Subject | Re: [PATCH 2/4] mm: thp: make deferred split shrinker memcg aware | From | Yang Shi <> | Date | Mon, 10 Jun 2019 10:23:06 -0700 |
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On 6/10/19 1:21 AM, Kirill Tkhai wrote: > Hi, Yang, > > On 07.06.2019 09:07, Yang Shi wrote: >> Currently THP deferred split shrinker is not memcg aware, this may cause >> premature OOM with some configuration. For example the below test would >> run into premature OOM easily: >> >> $ cgcreate -g memory:thp >> $ echo 4G > /sys/fs/cgroup/memory/thp/memory/limit_in_bytes >> $ cgexec -g memory:thp transhuge-stress 4000 >> >> transhuge-stress comes from kernel selftest. >> >> It is easy to hit OOM, but there are still a lot THP on the deferred >> split queue, memcg direct reclaim can't touch them since the deferred >> split shrinker is not memcg aware. >> >> Convert deferred split shrinker memcg aware by introducing per memcg >> deferred split queue. The THP should be on either per node or per memcg >> deferred split queue if it belongs to a memcg. When the page is >> immigrated to the other memcg, it will be immigrated to the target >> memcg's deferred split queue too. >> >> And, move deleting THP from deferred split queue in page free before >> memcg uncharge so that the page's memcg information is available. >> >> Reuse the second tail page's deferred_list for per memcg list since the >> same THP can't be on multiple deferred split queues. >> >> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> >> Cc: Johannes Weiner <hannes@cmpxchg.org> >> Cc: Michal Hocko <mhocko@suse.com> >> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> >> Cc: Hugh Dickins <hughd@google.com> >> Cc: Shakeel Butt <shakeelb@google.com> >> Cc: David Rientjes <rientjes@google.com> >> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com> >> --- >> include/linux/huge_mm.h | 15 ++++++++++ >> include/linux/memcontrol.h | 4 +++ >> include/linux/mm_types.h | 1 + >> mm/huge_memory.c | 71 +++++++++++++++++++++++++++++++++------------- >> mm/memcontrol.c | 19 +++++++++++++ >> mm/swap.c | 4 +++ >> 6 files changed, 94 insertions(+), 20 deletions(-) >> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index 7cd5c15..8137c3a 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -250,6 +250,17 @@ static inline bool thp_migration_supported(void) >> return IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION); >> } >> >> +static inline struct list_head *page_deferred_list(struct page *page) >> +{ >> + /* >> + * Global or memcg deferred list in the second tail pages is >> + * occupied by compound_head. >> + */ >> + return &page[2].deferred_list; >> +} >> + >> +extern void del_thp_from_deferred_split_queue(struct page *); >> + >> #else /* CONFIG_TRANSPARENT_HUGEPAGE */ >> #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) >> #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) >> @@ -368,6 +379,10 @@ static inline bool thp_migration_supported(void) >> { >> return false; >> } >> + >> +static inline void del_thp_from_deferred_split_queue(struct page *page) >> +{ >> +} >> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ >> >> #endif /* _LINUX_HUGE_MM_H */ >> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h >> index bc74d6a..5d3c10c 100644 >> --- a/include/linux/memcontrol.h >> +++ b/include/linux/memcontrol.h >> @@ -316,6 +316,10 @@ struct mem_cgroup { >> struct list_head event_list; >> spinlock_t event_list_lock; >> >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> + struct deferred_split deferred_split_queue; >> +#endif >> + >> struct mem_cgroup_per_node *nodeinfo[0]; >> /* WARNING: nodeinfo must be the last member here */ >> }; >> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >> index 8ec38b1..4eabf80 100644 >> --- a/include/linux/mm_types.h >> +++ b/include/linux/mm_types.h >> @@ -139,6 +139,7 @@ struct page { >> struct { /* Second tail page of compound page */ >> unsigned long _compound_pad_1; /* compound_head */ >> unsigned long _compound_pad_2; >> + /* For both global and memcg */ >> struct list_head deferred_list; >> }; >> struct { /* Page table pages */ >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 81cf759..3307697 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -492,10 +492,15 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) >> return pmd; >> } >> >> -static inline struct list_head *page_deferred_list(struct page *page) >> +static inline struct deferred_split *get_deferred_split_queue(struct page *page) >> { >> - /* ->lru in the tail pages is occupied by compound_head. */ >> - return &page[2].deferred_list; >> + struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; >> + struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); >> + >> + if (memcg) >> + return &memcg->deferred_split_queue; >> + else >> + return &pgdat->deferred_split_queue; > memory_cgrp_subsys is not early initialized, so at the beginning of boot > root_mem_cgroup is NULL, and pages will use &pgdat->deferred_split_queue > list head. But after root_mem_cgroup is initialized, another list head > will be used, won't it?! So there will be two different list heads used > for same cgroup. > > This may be a reason of a problem (I won't say you, where the problem will > occur).
Actually I was wondering this too. But, it looks impossible. The memcg is initialized by subsys_initcall, there are still fs, device and late initcalls after it. The init process is run much later, so I can't think of any THP could be put on deferred split queue before memcg is initialized. There may be compound page allocation, i.e. skb, but we don't care them.
> >> } >> >> void prep_transhuge_page(struct page *page) >> @@ -2658,7 +2663,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) >> { >> struct page *head = compound_head(page); >> struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); >> - struct deferred_split *ds_queue = &pgdata->deferred_split_queue; >> + struct deferred_split *ds_queue = get_deferred_split_queue(page); >> struct anon_vma *anon_vma = NULL; >> struct address_space *mapping = NULL; >> int count, mapcount, extra_pins, ret; >> @@ -2792,25 +2797,36 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) >> return ret; >> } >> >> -void free_transhuge_page(struct page *page) >> +void del_thp_from_deferred_split_queue(struct page *page) >> { >> - struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); >> - struct deferred_split *ds_queue = &pgdata->deferred_split_queue; >> - unsigned long flags; >> - >> - spin_lock_irqsave(&ds_queue->split_queue_lock, flags); >> - if (!list_empty(page_deferred_list(page))) { >> - ds_queue->split_queue_len--; >> - list_del(page_deferred_list(page)); >> + /* >> + * The THP may be not on LRU at this point, e.g. the old page of >> + * NUMA migration. And PageTransHuge is not enough to distinguish >> + * with other compound page, e.g. skb, THP destructor is not used >> + * anymore and will be removed, so the compound order sounds like >> + * the only choice here. >> + */ >> + if (PageTransHuge(page) && compound_order(page) == HPAGE_PMD_ORDER) { >> + struct deferred_split *ds_queue = get_deferred_split_queue(page); >> + unsigned long flags; >> + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); >> + if (!list_empty(page_deferred_list(page))) { >> + ds_queue->split_queue_len--; >> + list_del(page_deferred_list(page)); >> + } >> + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); >> } >> - spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); >> +} >> + >> +void free_transhuge_page(struct page *page) >> +{ >> free_compound_page(page); >> } >> >> void deferred_split_huge_page(struct page *page) >> { >> - struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); >> - struct deferred_split *ds_queue = &pgdata->deferred_split_queue; >> + struct deferred_split *ds_queue = get_deferred_split_queue(page); >> + struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; >> unsigned long flags; >> >> VM_BUG_ON_PAGE(!PageTransHuge(page), page); >> @@ -2820,6 +2836,9 @@ void deferred_split_huge_page(struct page *page) >> count_vm_event(THP_DEFERRED_SPLIT_PAGE); >> list_add_tail(page_deferred_list(page), &ds_queue->split_queue); >> ds_queue->split_queue_len++; >> + if (memcg) >> + memcg_set_shrinker_bit(memcg, page_to_nid(page), >> + deferred_split_shrinker.id); >> } >> spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); >> } >> @@ -2827,8 +2846,15 @@ void deferred_split_huge_page(struct page *page) >> static unsigned long deferred_split_count(struct shrinker *shrink, >> struct shrink_control *sc) >> { >> - struct pglist_data *pgdata = NODE_DATA(sc->nid); >> - struct deferred_split *ds_queue = &pgdata->deferred_split_queue; >> + struct deferred_split *ds_queue; >> + >> + if (!sc->memcg) { >> + struct pglist_data *pgdata = NODE_DATA(sc->nid); >> + ds_queue = &pgdata->deferred_split_queue; >> + return READ_ONCE(ds_queue->split_queue_len); >> + } >> + >> + ds_queue = &sc->memcg->deferred_split_queue; >> return READ_ONCE(ds_queue->split_queue_len); >> } >> >> @@ -2836,12 +2862,17 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, >> struct shrink_control *sc) >> { >> struct pglist_data *pgdata = NODE_DATA(sc->nid); >> - struct deferred_split *ds_queue = &pgdata->deferred_split_queue; >> + struct deferred_split *ds_queue; >> unsigned long flags; >> LIST_HEAD(list), *pos, *next; >> struct page *page; >> int split = 0; >> >> + if (sc->memcg) >> + ds_queue = &sc->memcg->deferred_split_queue; >> + else >> + ds_queue = &pgdata->deferred_split_queue; >> + >> spin_lock_irqsave(&ds_queue->split_queue_lock, flags); >> /* Take pin on all head pages to avoid freeing them under us */ >> list_for_each_safe(pos, next, &ds_queue->split_queue) { >> @@ -2888,7 +2919,7 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, >> .count_objects = deferred_split_count, >> .scan_objects = deferred_split_scan, >> .seeks = DEFAULT_SEEKS, >> - .flags = SHRINKER_NUMA_AWARE, >> + .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, >> }; >> >> #ifdef CONFIG_DEBUG_FS >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index e50a2db..fe7e544 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -4579,6 +4579,11 @@ static struct mem_cgroup *mem_cgroup_alloc(void) >> #ifdef CONFIG_CGROUP_WRITEBACK >> INIT_LIST_HEAD(&memcg->cgwb_list); >> #endif >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> + spin_lock_init(&memcg->deferred_split_queue.split_queue_lock); >> + INIT_LIST_HEAD(&memcg->deferred_split_queue.split_queue); >> + memcg->deferred_split_queue.split_queue_len = 0; >> +#endif >> idr_replace(&mem_cgroup_idr, memcg, memcg->id.id); >> return memcg; >> fail: >> @@ -4949,6 +4954,20 @@ static int mem_cgroup_move_account(struct page *page, >> __mod_memcg_state(to, NR_WRITEBACK, nr_pages); >> } >> >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> + if (compound && !list_empty(page_deferred_list(page))) { >> + spin_lock(&from->deferred_split_queue.split_queue_lock); >> + list_del(page_deferred_list(page)); >> + from->deferred_split_queue.split_queue_len--; >> + spin_unlock(&from->deferred_split_queue.split_queue_lock); > Won't be better to assign > > page->mem_cgroup = to; > > after removing from one list and before linking to another list? > There is possible no a problem, but another people writing code > on top of this may not expect such the behavior.
It should be fine too.
>> + spin_lock(&to->deferred_split_queue.split_queue_lock); >> + list_add_tail(page_deferred_list(page), >> + &to->deferred_split_queue.split_queue); >> + to->deferred_split_queue.split_queue_len++; >> + spin_unlock(&to->deferred_split_queue.split_queue_lock); >> + } >> +#endif >> /* >> * It is safe to change page->mem_cgroup here because the page >> * is referenced, charged, and isolated - we can't race with >> diff --git a/mm/swap.c b/mm/swap.c >> index 3a75722..3348295 100644 >> --- a/mm/swap.c >> +++ b/mm/swap.c >> @@ -69,6 +69,10 @@ static void __page_cache_release(struct page *page) >> del_page_from_lru_list(page, lruvec, page_off_lru(page)); >> spin_unlock_irqrestore(&pgdat->lru_lock, flags); >> } >> + >> + /* Delete THP from deferred split queue before memcg uncharge */ >> + del_thp_from_deferred_split_queue(page); >> + >> __ClearPageWaiters(page); >> mem_cgroup_uncharge(page); >> }
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