From 364c1eebe453f06f0c1e837eb155a5725c9cd272 Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Mon, 23 Sep 2019 15:38:06 -0700 Subject: [PATCH] mm: thp: extract split_queue_* into a struct Patch series "Make deferred split shrinker memcg aware", v6. 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. Reuse the second tail page's deferred_list for per memcg list since the same THP can't be on multiple deferred split queues. Make deferred split shrinker not depend on memcg kmem since it is not slab. It doesn't make sense to not shrink THP even though memcg kmem is disabled. With the above change the test demonstrated above doesn't trigger OOM even though with cgroup.memory=nokmem. This patch (of 4): Put split_queue, split_queue_lock and split_queue_len into a struct in order to reduce code duplication when we convert deferred_split to memcg aware in the later patches. Link: http://lkml.kernel.org/r/1565144277-36240-2-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Yang Shi Suggested-by: "Kirill A . Shutemov" Acked-by: Kirill A. Shutemov Reviewed-by: Kirill Tkhai Cc: Johannes Weiner Cc: Michal Hocko Cc: Hugh Dickins Cc: Shakeel Butt Cc: David Rientjes Cc: Qian Cai Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmzone.h | 12 ++++++++--- mm/huge_memory.c | 45 +++++++++++++++++++++++------------------- mm/page_alloc.c | 8 +++++--- 3 files changed, 39 insertions(+), 26 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index aafb7c38c627..bda20282746b 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -679,6 +679,14 @@ struct zonelist { extern struct page *mem_map; #endif +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +struct deferred_split { + spinlock_t split_queue_lock; + struct list_head split_queue; + unsigned long split_queue_len; +}; +#endif + /* * On NUMA machines, each NUMA node would have a pg_data_t to describe * it's memory layout. On UMA machines there is a single pglist_data which @@ -758,9 +766,7 @@ typedef struct pglist_data { #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */ #ifdef CONFIG_TRANSPARENT_HUGEPAGE - spinlock_t split_queue_lock; - struct list_head split_queue; - unsigned long split_queue_len; + struct deferred_split deferred_split_queue; #endif /* Fields commonly accessed by the page reclaim scanner */ diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 483b07b2d6ae..c642c0394690 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2691,6 +2691,7 @@ 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 anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; int count, mapcount, extra_pins, ret; @@ -2777,17 +2778,17 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) } /* Prevent deferred_split_scan() touching ->_refcount */ - spin_lock(&pgdata->split_queue_lock); + spin_lock(&ds_queue->split_queue_lock); count = page_count(head); mapcount = total_mapcount(head); if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { if (!list_empty(page_deferred_list(head))) { - pgdata->split_queue_len--; + ds_queue->split_queue_len--; list_del(page_deferred_list(head)); } if (mapping) __dec_node_page_state(page, NR_SHMEM_THPS); - spin_unlock(&pgdata->split_queue_lock); + spin_unlock(&ds_queue->split_queue_lock); __split_huge_page(page, list, end, flags); if (PageSwapCache(head)) { swp_entry_t entry = { .val = page_private(head) }; @@ -2804,7 +2805,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) dump_page(page, "total_mapcount(head) > 0"); BUG(); } - spin_unlock(&pgdata->split_queue_lock); + spin_unlock(&ds_queue->split_queue_lock); fail: if (mapping) xa_unlock(&mapping->i_pages); spin_unlock_irqrestore(&pgdata->lru_lock, flags); @@ -2827,52 +2828,56 @@ fail: if (mapping) void free_transhuge_page(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(&pgdata->split_queue_lock, flags); + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); if (!list_empty(page_deferred_list(page))) { - pgdata->split_queue_len--; + ds_queue->split_queue_len--; list_del(page_deferred_list(page)); } - spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 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; unsigned long flags; VM_BUG_ON_PAGE(!PageTransHuge(page), page); - spin_lock_irqsave(&pgdata->split_queue_lock, flags); + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); if (list_empty(page_deferred_list(page))) { count_vm_event(THP_DEFERRED_SPLIT_PAGE); - list_add_tail(page_deferred_list(page), &pgdata->split_queue); - pgdata->split_queue_len++; + list_add_tail(page_deferred_list(page), &ds_queue->split_queue); + ds_queue->split_queue_len++; } - spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); } static unsigned long deferred_split_count(struct shrinker *shrink, struct shrink_control *sc) { struct pglist_data *pgdata = NODE_DATA(sc->nid); - return READ_ONCE(pgdata->split_queue_len); + struct deferred_split *ds_queue = &pgdata->deferred_split_queue; + return READ_ONCE(ds_queue->split_queue_len); } 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; unsigned long flags; LIST_HEAD(list), *pos, *next; struct page *page; int split = 0; - spin_lock_irqsave(&pgdata->split_queue_lock, flags); + 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, &pgdata->split_queue) { + list_for_each_safe(pos, next, &ds_queue->split_queue) { page = list_entry((void *)pos, struct page, mapping); page = compound_head(page); if (get_page_unless_zero(page)) { @@ -2880,12 +2885,12 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, } else { /* We lost race with put_compound_page() */ list_del_init(page_deferred_list(page)); - pgdata->split_queue_len--; + ds_queue->split_queue_len--; } if (!--sc->nr_to_scan) break; } - spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); list_for_each_safe(pos, next, &list) { page = list_entry((void *)pos, struct page, mapping); @@ -2899,15 +2904,15 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, put_page(page); } - spin_lock_irqsave(&pgdata->split_queue_lock, flags); - list_splice_tail(&list, &pgdata->split_queue); - spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + list_splice_tail(&list, &ds_queue->split_queue); + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); /* * Stop shrinker if we didn't split any page, but the queue is empty. * This can happen if pages were freed under us. */ - if (!split && list_empty(&pgdata->split_queue)) + if (!split && list_empty(&ds_queue->split_queue)) return SHRINK_STOP; return split; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 591e026534c2..a41436cca563 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6646,9 +6646,11 @@ static unsigned long __init calc_memmap_size(unsigned long spanned_pages, #ifdef CONFIG_TRANSPARENT_HUGEPAGE static void pgdat_init_split_queue(struct pglist_data *pgdat) { - spin_lock_init(&pgdat->split_queue_lock); - INIT_LIST_HEAD(&pgdat->split_queue); - pgdat->split_queue_len = 0; + struct deferred_split *ds_queue = &pgdat->deferred_split_queue; + + spin_lock_init(&ds_queue->split_queue_lock); + INIT_LIST_HEAD(&ds_queue->split_queue); + ds_queue->split_queue_len = 0; } #else static void pgdat_init_split_queue(struct pglist_data *pgdat) {}