* [PATCH] mm: memcg/slab: introduce mem_cgroup_from_obj()
@ 2020-01-17 20:36 Roman Gushchin
2020-01-17 20:54 ` Shakeel Butt
0 siblings, 1 reply; 2+ messages in thread
From: Roman Gushchin @ 2020-01-17 20:36 UTC (permalink / raw)
To: linux-mm, Andrew Morton
Cc: Michal Hocko, Johannes Weiner, Shakeel Butt, Vladimir Davydov,
linux-kernel, kernel-team, Yafang Shao, Roman Gushchin
Sometimes we need to get a memcg pointer from a charged kernel object.
The right way to get it depends on whether it's a proper slab object
or it's backed by raw pages (e.g. it's a vmalloc alloction). In the
first case the kmem_cache->memcg_params.memcg indirection should be
used; in other cases it's just page->mem_cgroup.
To simplify this task and hide the implementation details let's
introduce a mem_cgroup_from_obj() helper, which takes a pointer
to any kernel object and returns a valid memcg pointer or NULL.
Passing a kernel address rather than a pointer to a page will allow
to use this helper for per-object (rather than per-page) tracked
objects in the future.
The caller is still responsible to ensure that the returned memcg
isn't going away underneath: take the rcu read lock, cgroup mutex etc;
depending on the context.
mem_cgroup_from_kmem() defined in mm/list_lru.c is now obsolete
and can be removed.
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
---
include/linux/memcontrol.h | 7 +++++++
mm/list_lru.c | 12 +-----------
mm/memcontrol.c | 32 +++++++++++++++++++++++++++++---
3 files changed, 37 insertions(+), 14 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a7a0a1a5c8d5..292729a1b8c6 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -420,6 +420,8 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *, struct pglist_data *);
struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
+struct mem_cgroup *mem_cgroup_from_obj(void *p);
+
struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm);
struct mem_cgroup *get_mem_cgroup_from_page(struct page *page);
@@ -912,6 +914,11 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
return true;
}
+static inline struct mem_cgroup *mem_cgroup_from_obj(void *p)
+{
+ return NULL;
+}
+
static inline struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
{
return NULL;
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 0f1f6b06b7f3..8de5e3784ee4 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -57,16 +57,6 @@ list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
return &nlru->lru;
}
-static __always_inline struct mem_cgroup *mem_cgroup_from_kmem(void *ptr)
-{
- struct page *page;
-
- if (!memcg_kmem_enabled())
- return NULL;
- page = virt_to_head_page(ptr);
- return memcg_from_slab_page(page);
-}
-
static inline struct list_lru_one *
list_lru_from_kmem(struct list_lru_node *nlru, void *ptr,
struct mem_cgroup **memcg_ptr)
@@ -77,7 +67,7 @@ list_lru_from_kmem(struct list_lru_node *nlru, void *ptr,
if (!nlru->memcg_lrus)
goto out;
- memcg = mem_cgroup_from_kmem(ptr);
+ memcg = mem_cgroup_from_obj(ptr);
if (!memcg)
goto out;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d4394ae4e5be..e768e8d87704 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -757,13 +757,12 @@ void __mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,
void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val)
{
- struct page *page = virt_to_head_page(p);
- pg_data_t *pgdat = page_pgdat(page);
+ pg_data_t *pgdat = page_pgdat(virt_to_page(p));
struct mem_cgroup *memcg;
struct lruvec *lruvec;
rcu_read_lock();
- memcg = memcg_from_slab_page(page);
+ memcg = mem_cgroup_from_obj(p);
/* Untracked pages have no memcg, no lruvec. Update only the node */
if (!memcg || memcg == root_mem_cgroup) {
@@ -2635,6 +2634,33 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
unlock_page_lru(page, isolated);
}
+/*
+ * Returns a pointer to the memory cgroup to which the kernel object is charged.
+ *
+ * The caller must ensure the memcg lifetime, e.g. by taking rcu_read_lock(),
+ * cgroup_mutex, etc.
+ */
+struct mem_cgroup *mem_cgroup_from_obj(void *p)
+{
+ struct page *page;
+
+ if (mem_cgroup_disabled())
+ return NULL;
+
+ page = virt_to_head_page(p);
+
+ /*
+ * Slab pages don't have page->mem_cgroup set because corresponding
+ * kmem caches can be reparented during the lifetime. That's why
+ * memcg_from_slab_page() should be used instead.
+ */
+ if (PageSlab(page))
+ return memcg_from_slab_page(page);
+
+ /* All other pages use page->mem_cgroup */
+ return page->mem_cgroup;
+}
+
#ifdef CONFIG_MEMCG_KMEM
static int memcg_alloc_cache_id(void)
{
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] mm: memcg/slab: introduce mem_cgroup_from_obj()
2020-01-17 20:36 [PATCH] mm: memcg/slab: introduce mem_cgroup_from_obj() Roman Gushchin
@ 2020-01-17 20:54 ` Shakeel Butt
0 siblings, 0 replies; 2+ messages in thread
From: Shakeel Butt @ 2020-01-17 20:54 UTC (permalink / raw)
To: Roman Gushchin
Cc: Linux MM, Andrew Morton, Michal Hocko, Johannes Weiner,
Vladimir Davydov, LKML, Kernel Team, Yafang Shao
On Fri, Jan 17, 2020 at 12:36 PM Roman Gushchin <guro@fb.com> wrote:
>
> Sometimes we need to get a memcg pointer from a charged kernel object.
> The right way to get it depends on whether it's a proper slab object
> or it's backed by raw pages (e.g. it's a vmalloc alloction). In the
> first case the kmem_cache->memcg_params.memcg indirection should be
> used; in other cases it's just page->mem_cgroup.
>
> To simplify this task and hide the implementation details let's
> introduce a mem_cgroup_from_obj() helper, which takes a pointer
> to any kernel object and returns a valid memcg pointer or NULL.
>
> Passing a kernel address rather than a pointer to a page will allow
> to use this helper for per-object (rather than per-page) tracked
> objects in the future.
>
> The caller is still responsible to ensure that the returned memcg
> isn't going away underneath: take the rcu read lock, cgroup mutex etc;
> depending on the context.
>
> mem_cgroup_from_kmem() defined in mm/list_lru.c is now obsolete
> and can be removed.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Acked-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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