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mm: memcontrol/slab: Use helpers to access slab page's memcg_data

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To gather all direct accesses to struct page's memcg_data field in one
place, let's introduce 3 new helpers to use in the slab accounting code:

  struct obj_cgroup **page_objcgs(struct page *page);
  struct obj_cgroup **page_objcgs_check(struct page *page);
  bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs);

They are similar to the corresponding API for generic pages, except that
the setter can return false, indicating that the value has been already
set from a different thread.

Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/20201027001657.3398190-3-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-3-guro@fb.com
This commit is contained in:
Roman Gushchin 2020-12-01 13:58:28 -08:00 committed by Alexei Starovoitov
parent bcfe06bf26
commit 270c6a7146
3 changed files with 75 additions and 30 deletions
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64
include/linux/memcontrol.h
View File

@ -416,6 +416,70 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
return (struct mem_cgroup *)memcg_data;
}
#ifdef CONFIG_MEMCG_KMEM
/*
* page_objcgs - get the object cgroups vector associated with a page
* @page: a pointer to the page struct
*
* Returns a pointer to the object cgroups vector associated with the page,
* or NULL. This function assumes that the page is known to have an
* associated object cgroups vector. It's not safe to call this function
* against pages, which might have an associated memory cgroup: e.g.
* kernel stack pages.
*/
static inline struct obj_cgroup **page_objcgs(struct page *page)
{
return (struct obj_cgroup **)(READ_ONCE(page->memcg_data) & ~0x1UL);
}
/*
* page_objcgs_check - get the object cgroups vector associated with a page
* @page: a pointer to the page struct
*
* Returns a pointer to the object cgroups vector associated with the page,
* or NULL. This function is safe to use if the page can be directly associated
* with a memory cgroup.
*/
static inline struct obj_cgroup **page_objcgs_check(struct page *page)
{
unsigned long memcg_data = READ_ONCE(page->memcg_data);
if (memcg_data && (memcg_data & 0x1UL))
return (struct obj_cgroup **)(memcg_data & ~0x1UL);
return NULL;
}
/*
* set_page_objcgs - associate a page with a object cgroups vector
* @page: a pointer to the page struct
* @objcgs: a pointer to the object cgroups vector
*
* Atomically associates a page with a vector of object cgroups.
*/
static inline bool set_page_objcgs(struct page *page,
struct obj_cgroup **objcgs)
{
return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL);
}
#else
static inline struct obj_cgroup **page_objcgs(struct page *page)
{
return NULL;
}
static inline struct obj_cgroup **page_objcgs_check(struct page *page)
{
return NULL;
}
static inline bool set_page_objcgs(struct page *page,
struct obj_cgroup **objcgs)
{
return true;
}
#endif
static __always_inline bool memcg_stat_item_in_bytes(int idx)
{
if (idx == MEMCG_PERCPU_B)

6
mm/memcontrol.c
View File

@ -2899,7 +2899,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
if (!vec)
return -ENOMEM;
if (cmpxchg(&page->memcg_data, 0, (unsigned long)vec | 0x1UL))
if (!set_page_objcgs(page, vec))
kfree(vec);
else
kmemleak_not_leak(vec);
@ -2933,12 +2933,12 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p)
* Memcg membership data for each individual object is saved in
* the page->obj_cgroups.
*/
if (page_has_obj_cgroups(page)) {
if (page_objcgs_check(page)) {
struct obj_cgroup *objcg;
unsigned int off;
off = obj_to_index(page->slab_cache, page, p);
objcg = page_obj_cgroups(page)[off];
objcg = page_objcgs(page)[off];
if (objcg)
return obj_cgroup_memcg(objcg);

35
mm/slab.h
View File

@ -239,28 +239,12 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla
}
#ifdef CONFIG_MEMCG_KMEM
static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
{
/*
* Page's memory cgroup and obj_cgroups vector are sharing the same
* space. To distinguish between them in case we don't know for sure
* that the page is a slab page (e.g. page_cgroup_ino()), let's
* always set the lowest bit of obj_cgroups.
*/
return (struct obj_cgroup **)(page->memcg_data & ~0x1UL);
}
static inline bool page_has_obj_cgroups(struct page *page)
{
return page->memcg_data & 0x1UL;
}
int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
gfp_t gfp);
static inline void memcg_free_page_obj_cgroups(struct page *page)
{
kfree(page_obj_cgroups(page));
kfree(page_objcgs(page));
page->memcg_data = 0;
}
@ -322,7 +306,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
if (likely(p[i])) {
page = virt_to_head_page(p[i]);
if (!page_has_obj_cgroups(page) &&
if (!page_objcgs(page) &&
memcg_alloc_page_obj_cgroups(page, s, flags)) {
obj_cgroup_uncharge(objcg, obj_full_size(s));
continue;
@ -330,7 +314,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
off = obj_to_index(s, page, p[i]);
obj_cgroup_get(objcg);
page_obj_cgroups(page)[off] = objcg;
page_objcgs(page)[off] = objcg;
mod_objcg_state(objcg, page_pgdat(page),
cache_vmstat_idx(s), obj_full_size(s));
} else {
@ -344,6 +328,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
void **p, int objects)
{
struct kmem_cache *s;
struct obj_cgroup **objcgs;
struct obj_cgroup *objcg;
struct page *page;
unsigned int off;
@ -357,7 +342,8 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
continue;
page = virt_to_head_page(p[i]);
if (!page_has_obj_cgroups(page))
objcgs = page_objcgs(page);
if (!objcgs)
continue;
if (!s_orig)
@ -366,11 +352,11 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
s = s_orig;
off = obj_to_index(s, page, p[i]);
objcg = page_obj_cgroups(page)[off];
objcg = objcgs[off];
if (!objcg)
continue;
page_obj_cgroups(page)[off] = NULL;
objcgs[off] = NULL;
obj_cgroup_uncharge(objcg, obj_full_size(s));
mod_objcg_state(objcg, page_pgdat(page), cache_vmstat_idx(s),
-obj_full_size(s));
@ -379,11 +365,6 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
}
#else /* CONFIG_MEMCG_KMEM */
static inline bool page_has_obj_cgroups(struct page *page)
{
return false;
}
static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr)
{
return NULL;