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 <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/buffer.c b/fs/buffer.c
index c8c2b7d..4cc679d5 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -45,6 +45,7 @@
#include <linux/mpage.h>
#include <linux/bit_spinlock.h>
#include <linux/pagevec.h>
+#include <linux/sched/mm.h>
#include <trace/events/block.h>
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 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
} 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 121e218..50e3e80 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 bf9cf73..c071af1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -714,6 +714,28 @@ 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.
*/
static __always_inline struct mem_cgroup *get_mem_cgroup_from_current(void)
