Commit f7ce3190 authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
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slab: embed memcg_cache_params to kmem_cache



Currently, kmem_cache stores a pointer to struct memcg_cache_params
instead of embedding it.  The rationale is to save memory when kmem
accounting is disabled.  However, the memcg_cache_params has shrivelled
drastically since it was first introduced:

* Initially:

struct memcg_cache_params {
	bool is_root_cache;
	union {
		struct kmem_cache *memcg_caches[0];
		struct {
			struct mem_cgroup *memcg;
			struct list_head list;
			struct kmem_cache *root_cache;
			bool dead;
			atomic_t nr_pages;
			struct work_struct destroy;
		};
	};
};

* Now:

struct memcg_cache_params {
	bool is_root_cache;
	union {
		struct {
			struct rcu_head rcu_head;
			struct kmem_cache *memcg_caches[0];
		};
		struct {
			struct mem_cgroup *memcg;
			struct kmem_cache *root_cache;
		};
	};
};

So the memory saving does not seem to be a clear win anymore.

OTOH, keeping a pointer to memcg_cache_params struct instead of embedding
it results in touching one more cache line on kmem alloc/free hot paths.
Besides, it makes linking kmem caches in a list chained by a field of
struct memcg_cache_params really painful due to a level of indirection,
while I want to make them linked in the following patch.  That said, let
us embed it.
Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 49e7e7ff
......@@ -473,14 +473,14 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
#ifndef ARCH_SLAB_MINALIGN
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
#endif
struct memcg_cache_array {
struct rcu_head rcu;
struct kmem_cache *entries[0];
};
/*
* This is the main placeholder for memcg-related information in kmem caches.
* struct kmem_cache will hold a pointer to it, so the memory cost while
* disabled is 1 pointer. The runtime cost while enabled, gets bigger than it
* would otherwise be if that would be bundled in kmem_cache: we'll need an
* extra pointer chase. But the trade off clearly lays in favor of not
* penalizing non-users.
*
* Both the root cache and the child caches will have it. For the root cache,
* this will hold a dynamically allocated array large enough to hold
* information about the currently limited memcgs in the system. To allow the
......@@ -495,10 +495,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
struct memcg_cache_params {
bool is_root_cache;
union {
struct {
struct rcu_head rcu_head;
struct kmem_cache *memcg_caches[0];
};
struct memcg_cache_array __rcu *memcg_caches;
struct {
struct mem_cgroup *memcg;
struct kmem_cache *root_cache;
......
......@@ -70,7 +70,7 @@ struct kmem_cache {
int obj_offset;
#endif /* CONFIG_DEBUG_SLAB */
#ifdef CONFIG_MEMCG_KMEM
struct memcg_cache_params *memcg_params;
struct memcg_cache_params memcg_params;
#endif
struct kmem_cache_node *node[MAX_NUMNODES];
......
......@@ -85,7 +85,7 @@ struct kmem_cache {
struct kobject kobj; /* For sysfs */
#endif
#ifdef CONFIG_MEMCG_KMEM
struct memcg_cache_params *memcg_params;
struct memcg_cache_params memcg_params;
int max_attr_size; /* for propagation, maximum size of a stored attr */
#ifdef CONFIG_SYSFS
struct kset *memcg_kset;
......
......@@ -332,7 +332,7 @@ struct mem_cgroup {
struct cg_proto tcp_mem;
#endif
#if defined(CONFIG_MEMCG_KMEM)
/* Index in the kmem_cache->memcg_params->memcg_caches array */
/* Index in the kmem_cache->memcg_params.memcg_caches array */
int kmemcg_id;
#endif
......@@ -531,7 +531,7 @@ static void disarm_sock_keys(struct mem_cgroup *memcg)
#ifdef CONFIG_MEMCG_KMEM
/*
* This will be the memcg's index in each cache's ->memcg_params->memcg_caches.
* This will be the memcg's index in each cache's ->memcg_params.memcg_caches.
* The main reason for not using cgroup id for this:
* this works better in sparse environments, where we have a lot of memcgs,
* but only a few kmem-limited. Or also, if we have, for instance, 200
......@@ -2667,8 +2667,7 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep)
struct mem_cgroup *memcg;
struct kmem_cache *memcg_cachep;
VM_BUG_ON(!cachep->memcg_params);
VM_BUG_ON(!cachep->memcg_params->is_root_cache);
VM_BUG_ON(!is_root_cache(cachep));
if (current->memcg_kmem_skip_account)
return cachep;
......@@ -2702,7 +2701,7 @@ out:
void __memcg_kmem_put_cache(struct kmem_cache *cachep)
{
if (!is_root_cache(cachep))
css_put(&cachep->memcg_params->memcg->css);
css_put(&cachep->memcg_params.memcg->css);
}
/*
......@@ -2778,7 +2777,7 @@ struct mem_cgroup *__mem_cgroup_from_kmem(void *ptr)
if (PageSlab(page)) {
cachep = page->slab_cache;
if (!is_root_cache(cachep))
memcg = cachep->memcg_params->memcg;
memcg = cachep->memcg_params.memcg;
} else
/* page allocated by alloc_kmem_pages */
memcg = page->mem_cgroup;
......
......@@ -86,8 +86,6 @@ extern struct kmem_cache *create_kmalloc_cache(const char *name, size_t size,
extern void create_boot_cache(struct kmem_cache *, const char *name,
size_t size, unsigned long flags);
struct mem_cgroup;
int slab_unmergeable(struct kmem_cache *s);
struct kmem_cache *find_mergeable(size_t size, size_t align,
unsigned long flags, const char *name, void (*ctor)(void *));
......@@ -167,14 +165,13 @@ ssize_t slabinfo_write(struct file *file, const char __user *buffer,
#ifdef CONFIG_MEMCG_KMEM
static inline bool is_root_cache(struct kmem_cache *s)
{
return !s->memcg_params || s->memcg_params->is_root_cache;
return s->memcg_params.is_root_cache;
}
static inline bool slab_equal_or_root(struct kmem_cache *s,
struct kmem_cache *p)
struct kmem_cache *p)
{
return (p == s) ||
(s->memcg_params && (p == s->memcg_params->root_cache));
return p == s || p == s->memcg_params.root_cache;
}
/*
......@@ -185,37 +182,30 @@ static inline bool slab_equal_or_root(struct kmem_cache *s,
static inline const char *cache_name(struct kmem_cache *s)
{
if (!is_root_cache(s))
return s->memcg_params->root_cache->name;
s = s->memcg_params.root_cache;
return s->name;
}
/*
* Note, we protect with RCU only the memcg_caches array, not per-memcg caches.
* That said the caller must assure the memcg's cache won't go away. Since once
* created a memcg's cache is destroyed only along with the root cache, it is
* true if we are going to allocate from the cache or hold a reference to the
* root cache by other means. Otherwise, we should hold either the slab_mutex
* or the memcg's slab_caches_mutex while calling this function and accessing
* the returned value.
* That said the caller must assure the memcg's cache won't go away by either
* taking a css reference to the owner cgroup, or holding the slab_mutex.
*/
static inline struct kmem_cache *
cache_from_memcg_idx(struct kmem_cache *s, int idx)
{
struct kmem_cache *cachep;
struct memcg_cache_params *params;
if (!s->memcg_params)
return NULL;
struct memcg_cache_array *arr;
rcu_read_lock();
params = rcu_dereference(s->memcg_params);
arr = rcu_dereference(s->memcg_params.memcg_caches);
/*
* Make sure we will access the up-to-date value. The code updating
* memcg_caches issues a write barrier to match this (see
* memcg_register_cache()).
* memcg_create_kmem_cache()).
*/
cachep = lockless_dereference(params->memcg_caches[idx]);
cachep = lockless_dereference(arr->entries[idx]);
rcu_read_unlock();
return cachep;
......@@ -225,7 +215,7 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
{
if (is_root_cache(s))
return s;
return s->memcg_params->root_cache;
return s->memcg_params.root_cache;
}
static __always_inline int memcg_charge_slab(struct kmem_cache *s,
......@@ -235,7 +225,7 @@ static __always_inline int memcg_charge_slab(struct kmem_cache *s,
return 0;
if (is_root_cache(s))
return 0;
return memcg_charge_kmem(s->memcg_params->memcg, gfp, 1 << order);
return memcg_charge_kmem(s->memcg_params.memcg, gfp, 1 << order);
}
static __always_inline void memcg_uncharge_slab(struct kmem_cache *s, int order)
......@@ -244,9 +234,13 @@ static __always_inline void memcg_uncharge_slab(struct kmem_cache *s, int order)
return;
if (is_root_cache(s))
return;
memcg_uncharge_kmem(s->memcg_params->memcg, 1 << order);
memcg_uncharge_kmem(s->memcg_params.memcg, 1 << order);
}
#else
extern void slab_init_memcg_params(struct kmem_cache *);
#else /* !CONFIG_MEMCG_KMEM */
static inline bool is_root_cache(struct kmem_cache *s)
{
return true;
......@@ -282,7 +276,11 @@ static inline int memcg_charge_slab(struct kmem_cache *s, gfp_t gfp, int order)
static inline void memcg_uncharge_slab(struct kmem_cache *s, int order)
{
}
#endif
static inline void slab_init_memcg_params(struct kmem_cache *s)
{
}
#endif /* CONFIG_MEMCG_KMEM */
static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
{
......
......@@ -106,62 +106,66 @@ static inline int kmem_cache_sanity_check(const char *name, size_t size)
#endif
#ifdef CONFIG_MEMCG_KMEM
static int memcg_alloc_cache_params(struct mem_cgroup *memcg,
struct kmem_cache *s, struct kmem_cache *root_cache)
void slab_init_memcg_params(struct kmem_cache *s)
{
size_t size;
s->memcg_params.is_root_cache = true;
RCU_INIT_POINTER(s->memcg_params.memcg_caches, NULL);
}
static int init_memcg_params(struct kmem_cache *s,
struct mem_cgroup *memcg, struct kmem_cache *root_cache)
{
struct memcg_cache_array *arr;
if (!memcg_kmem_enabled())
if (memcg) {
s->memcg_params.is_root_cache = false;
s->memcg_params.memcg = memcg;
s->memcg_params.root_cache = root_cache;
return 0;
}
if (!memcg) {
size = offsetof(struct memcg_cache_params, memcg_caches);
size += memcg_nr_cache_ids * sizeof(void *);
} else
size = sizeof(struct memcg_cache_params);
slab_init_memcg_params(s);
s->memcg_params = kzalloc(size, GFP_KERNEL);
if (!s->memcg_params)
return -ENOMEM;
if (!memcg_nr_cache_ids)
return 0;
if (memcg) {
s->memcg_params->memcg = memcg;
s->memcg_params->root_cache = root_cache;
} else
s->memcg_params->is_root_cache = true;
arr = kzalloc(sizeof(struct memcg_cache_array) +
memcg_nr_cache_ids * sizeof(void *),
GFP_KERNEL);
if (!arr)
return -ENOMEM;
RCU_INIT_POINTER(s->memcg_params.memcg_caches, arr);
return 0;
}
static void memcg_free_cache_params(struct kmem_cache *s)
static void destroy_memcg_params(struct kmem_cache *s)
{
kfree(s->memcg_params);
if (is_root_cache(s))
kfree(rcu_access_pointer(s->memcg_params.memcg_caches));
}
static int memcg_update_cache_params(struct kmem_cache *s, int num_memcgs)
static int update_memcg_params(struct kmem_cache *s, int new_array_size)
{
int size;
struct memcg_cache_params *new_params, *cur_params;
struct memcg_cache_array *old, *new;
BUG_ON(!is_root_cache(s));
size = offsetof(struct memcg_cache_params, memcg_caches);
size += num_memcgs * sizeof(void *);
if (!is_root_cache(s))
return 0;
new_params = kzalloc(size, GFP_KERNEL);
if (!new_params)
new = kzalloc(sizeof(struct memcg_cache_array) +
new_array_size * sizeof(void *), GFP_KERNEL);
if (!new)
return -ENOMEM;
cur_params = s->memcg_params;
memcpy(new_params->memcg_caches, cur_params->memcg_caches,
memcg_nr_cache_ids * sizeof(void *));
new_params->is_root_cache = true;
rcu_assign_pointer(s->memcg_params, new_params);
if (cur_params)
kfree_rcu(cur_params, rcu_head);
old = rcu_dereference_protected(s->memcg_params.memcg_caches,
lockdep_is_held(&slab_mutex));
if (old)
memcpy(new->entries, old->entries,
memcg_nr_cache_ids * sizeof(void *));
rcu_assign_pointer(s->memcg_params.memcg_caches, new);
if (old)
kfree_rcu(old, rcu);
return 0;
}
......@@ -172,10 +176,7 @@ int memcg_update_all_caches(int num_memcgs)
mutex_lock(&slab_mutex);
list_for_each_entry(s, &slab_caches, list) {
if (!is_root_cache(s))
continue;
ret = memcg_update_cache_params(s, num_memcgs);
ret = update_memcg_params(s, num_memcgs);
/*
* Instead of freeing the memory, we'll just leave the caches
* up to this point in an updated state.
......@@ -187,13 +188,13 @@ int memcg_update_all_caches(int num_memcgs)
return ret;
}
#else
static inline int memcg_alloc_cache_params(struct mem_cgroup *memcg,
struct kmem_cache *s, struct kmem_cache *root_cache)
static inline int init_memcg_params(struct kmem_cache *s,
struct mem_cgroup *memcg, struct kmem_cache *root_cache)
{
return 0;
}
static inline void memcg_free_cache_params(struct kmem_cache *s)
static inline void destroy_memcg_params(struct kmem_cache *s)
{
}
#endif /* CONFIG_MEMCG_KMEM */
......@@ -311,7 +312,7 @@ do_kmem_cache_create(char *name, size_t object_size, size_t size, size_t align,
s->align = align;
s->ctor = ctor;
err = memcg_alloc_cache_params(memcg, s, root_cache);
err = init_memcg_params(s, memcg, root_cache);
if (err)
goto out_free_cache;
......@@ -327,7 +328,7 @@ out:
return s;
out_free_cache:
memcg_free_cache_params(s);
destroy_memcg_params(s);
kmem_cache_free(kmem_cache, s);
goto out;
}
......@@ -439,11 +440,15 @@ static int do_kmem_cache_shutdown(struct kmem_cache *s,
#ifdef CONFIG_MEMCG_KMEM
if (!is_root_cache(s)) {
struct kmem_cache *root_cache = s->memcg_params->root_cache;
int memcg_id = memcg_cache_id(s->memcg_params->memcg);
BUG_ON(root_cache->memcg_params->memcg_caches[memcg_id] != s);
root_cache->memcg_params->memcg_caches[memcg_id] = NULL;
int idx;
struct memcg_cache_array *arr;
idx = memcg_cache_id(s->memcg_params.memcg);
arr = rcu_dereference_protected(s->memcg_params.root_cache->
memcg_params.memcg_caches,
lockdep_is_held(&slab_mutex));
BUG_ON(arr->entries[idx] != s);
arr->entries[idx] = NULL;
}
#endif
list_move(&s->list, release);
......@@ -481,27 +486,32 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
struct kmem_cache *root_cache)
{
static char memcg_name_buf[NAME_MAX + 1]; /* protected by slab_mutex */
int memcg_id = memcg_cache_id(memcg);
struct memcg_cache_array *arr;
struct kmem_cache *s = NULL;
char *cache_name;
int idx;
get_online_cpus();
get_online_mems();
mutex_lock(&slab_mutex);
idx = memcg_cache_id(memcg);
arr = rcu_dereference_protected(root_cache->memcg_params.memcg_caches,
lockdep_is_held(&slab_mutex));
/*
* Since per-memcg caches are created asynchronously on first
* allocation (see memcg_kmem_get_cache()), several threads can try to
* create the same cache, but only one of them may succeed.
*/
if (cache_from_memcg_idx(root_cache, memcg_id))
if (arr->entries[idx])
goto out_unlock;
cgroup_name(mem_cgroup_css(memcg)->cgroup,
memcg_name_buf, sizeof(memcg_name_buf));
cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
memcg_cache_id(memcg), memcg_name_buf);
idx, memcg_name_buf);
if (!cache_name)
goto out_unlock;
......@@ -525,7 +535,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
* initialized.
*/
smp_wmb();
root_cache->memcg_params->memcg_caches[memcg_id] = s;
arr->entries[idx] = s;
out_unlock:
mutex_unlock(&slab_mutex);
......@@ -545,7 +555,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *memcg)
mutex_lock(&slab_mutex);
list_for_each_entry_safe(s, s2, &slab_caches, list) {
if (is_root_cache(s) || s->memcg_params->memcg != memcg)
if (is_root_cache(s) || s->memcg_params.memcg != memcg)
continue;
/*
* The cgroup is about to be freed and therefore has no charges
......@@ -564,7 +574,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *memcg)
void slab_kmem_cache_release(struct kmem_cache *s)
{
memcg_free_cache_params(s);
destroy_memcg_params(s);
kfree(s->name);
kmem_cache_free(kmem_cache, s);
}
......@@ -640,6 +650,9 @@ void __init create_boot_cache(struct kmem_cache *s, const char *name, size_t siz
s->name = name;
s->size = s->object_size = size;
s->align = calculate_alignment(flags, ARCH_KMALLOC_MINALIGN, size);
slab_init_memcg_params(s);
err = __kmem_cache_create(s, flags);
if (err)
......@@ -980,7 +993,7 @@ int memcg_slab_show(struct seq_file *m, void *p)
if (p == slab_caches.next)
print_slabinfo_header(m);
if (!is_root_cache(s) && s->memcg_params->memcg == memcg)
if (!is_root_cache(s) && s->memcg_params.memcg == memcg)
cache_show(s, m);
return 0;
}
......
......@@ -3577,6 +3577,7 @@ static struct kmem_cache * __init bootstrap(struct kmem_cache *static_cache)
p->slab_cache = s;
#endif
}
slab_init_memcg_params(s);
list_add(&s->list, &slab_caches);
return s;
}
......@@ -4964,7 +4965,7 @@ static void memcg_propagate_slab_attrs(struct kmem_cache *s)
if (is_root_cache(s))
return;
root_cache = s->memcg_params->root_cache;
root_cache = s->memcg_params.root_cache;
/*
* This mean this cache had no attribute written. Therefore, no point
......@@ -5044,7 +5045,7 @@ static inline struct kset *cache_kset(struct kmem_cache *s)
{
#ifdef CONFIG_MEMCG_KMEM
if (!is_root_cache(s))
return s->memcg_params->root_cache->memcg_kset;
return s->memcg_params.root_cache->memcg_kset;
#endif
return slab_kset;
}
......
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