From f745c6f5fe75734f3b35d9d4e6ebe2a7d010ddda Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Fri, 17 Aug 2018 15:46:44 -0700 Subject: [PATCH] fs, mm: account buffer_head to kmemcg The buffer_head can consume a significant amount of system memory and is directly related to the amount of page cache. In our production environment we have observed that a lot of machines are spending a significant amount of memory as buffer_head and can not be left as system memory overhead. Charging buffer_head is not as simple as adding __GFP_ACCOUNT to the allocation. The buffer_heads can be allocated in a memcg different from the memcg of the page for which buffer_heads are being allocated. One concrete example is memory reclaim. The reclaim can trigger I/O of pages of any memcg on the system. So, the right way to charge buffer_head is to extract the memcg from the page for which buffer_heads are being allocated and then use targeted memcg charging API. [shakeelb@google.com: use __GFP_ACCOUNT for directed memcg charging] Link: http://lkml.kernel.org/r/20180702220208.213380-1-shakeelb@google.com Link: http://lkml.kernel.org/r/20180627191250.209150-3-shakeelb@google.com Signed-off-by: Shakeel Butt Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Jan Kara Cc: Amir Goldstein Cc: Greg Thelen Cc: Vladimir Davydov Cc: Roman Gushchin Cc: Alexander Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/buffer.c | 12 ++++++++++-- include/linux/memcontrol.h | 7 +++++++ mm/memcontrol.c | 22 ++++++++++++++++++++++ 3 files changed, 39 insertions(+), 2 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index c8c2b7d8b8d6..4cc679d5bf58 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -45,6 +45,7 @@ #include #include #include +#include #include static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); @@ -813,12 +814,16 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, bool retry) { struct buffer_head *bh, *head; - gfp_t gfp = GFP_NOFS; + gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT; long offset; + struct mem_cgroup *memcg; if (retry) gfp |= __GFP_NOFAIL; + memcg = get_mem_cgroup_from_page(page); + memalloc_use_memcg(memcg); + head = NULL; offset = PAGE_SIZE; while ((offset -= size) >= 0) { @@ -835,6 +840,9 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, /* Link the buffer to its page */ set_bh_page(bh, page, offset); } +out: + memalloc_unuse_memcg(); + mem_cgroup_put(memcg); return head; /* * In case anything failed, we just free everything we got. @@ -848,7 +856,7 @@ no_grow: } while (head); } - return NULL; + goto out; } EXPORT_SYMBOL_GPL(alloc_page_buffers); diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 121e218d2a21..50e3e807b427 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -375,6 +375,8 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p); struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm); +struct mem_cgroup *get_mem_cgroup_from_page(struct page *page); + static inline struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css){ return css ? container_of(css, struct mem_cgroup, css) : NULL; @@ -863,6 +865,11 @@ static inline struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm) return NULL; } +static inline struct mem_cgroup *get_mem_cgroup_from_page(struct page *page) +{ + return NULL; +} + static inline void mem_cgroup_put(struct mem_cgroup *memcg) { } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index bf9cf738c836..c071af193986 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -713,6 +713,28 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm) } EXPORT_SYMBOL(get_mem_cgroup_from_mm); +/** + * get_mem_cgroup_from_page: Obtain a reference on given page's memcg. + * @page: page from which memcg should be extracted. + * + * Obtain a reference on page->memcg and returns it if successful. Otherwise + * root_mem_cgroup is returned. + */ +struct mem_cgroup *get_mem_cgroup_from_page(struct page *page) +{ + struct mem_cgroup *memcg = page->mem_cgroup; + + if (mem_cgroup_disabled()) + return NULL; + + rcu_read_lock(); + if (!memcg || !css_tryget_online(&memcg->css)) + memcg = root_mem_cgroup; + rcu_read_unlock(); + return memcg; +} +EXPORT_SYMBOL(get_mem_cgroup_from_page); + /** * If current->active_memcg is non-NULL, do not fallback to current->mm->memcg. */