![Vladimir Davydov](/assets/img/avatar_default.png)
When a kmem cache is created (kmem_cache_create_memcg()), we first try to find a compatible cache that already exists and can handle requests from the new cache, i.e. has the same object size, alignment, ctor, etc. If there is such a cache, we do not create any new caches, instead we simply increment the refcount of the cache found and return it. Currently we do this procedure not only when creating root caches, but also for memcg caches. However, there is no point in that, because, as every memcg cache has exactly the same parameters as its parent and cache merging cannot be turned off in runtime (only on boot by passing "slub_nomerge"), the root caches of any two potentially mergeable memcg caches should be merged already, i.e. it must be the same root cache, and therefore we couldn't even get to the memcg cache creation, because it already exists. The only exception is boot caches - they are explicitly forbidden to be merged by setting their refcount to -1. There are currently only two of them - kmem_cache and kmem_cache_node, which are used in slab internals (I do not count kmalloc caches as their refcount is set to 1 immediately after creation). Since they are prevented from merging preliminary I guess we should avoid to merge their children too. So let's remove the useless code responsible for merging memcg caches. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: David Rientjes <rientjes@google.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Glauber Costa <glommer@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
292 lines
7.8 KiB
C
292 lines
7.8 KiB
C
#ifndef MM_SLAB_H
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#define MM_SLAB_H
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/*
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* Internal slab definitions
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*/
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/*
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* State of the slab allocator.
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*
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* This is used to describe the states of the allocator during bootup.
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* Allocators use this to gradually bootstrap themselves. Most allocators
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* have the problem that the structures used for managing slab caches are
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* allocated from slab caches themselves.
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*/
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enum slab_state {
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DOWN, /* No slab functionality yet */
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PARTIAL, /* SLUB: kmem_cache_node available */
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PARTIAL_ARRAYCACHE, /* SLAB: kmalloc size for arraycache available */
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PARTIAL_NODE, /* SLAB: kmalloc size for node struct available */
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UP, /* Slab caches usable but not all extras yet */
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FULL /* Everything is working */
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};
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extern enum slab_state slab_state;
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/* The slab cache mutex protects the management structures during changes */
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extern struct mutex slab_mutex;
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/* The list of all slab caches on the system */
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extern struct list_head slab_caches;
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/* The slab cache that manages slab cache information */
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extern struct kmem_cache *kmem_cache;
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unsigned long calculate_alignment(unsigned long flags,
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unsigned long align, unsigned long size);
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#ifndef CONFIG_SLOB
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/* Kmalloc array related functions */
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void create_kmalloc_caches(unsigned long);
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/* Find the kmalloc slab corresponding for a certain size */
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struct kmem_cache *kmalloc_slab(size_t, gfp_t);
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#endif
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/* Functions provided by the slab allocators */
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extern int __kmem_cache_create(struct kmem_cache *, unsigned long flags);
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extern struct kmem_cache *create_kmalloc_cache(const char *name, size_t size,
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unsigned long flags);
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extern void create_boot_cache(struct kmem_cache *, const char *name,
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size_t size, unsigned long flags);
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struct mem_cgroup;
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#ifdef CONFIG_SLUB
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struct kmem_cache *
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__kmem_cache_alias(const char *name, size_t size, size_t align,
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unsigned long flags, void (*ctor)(void *));
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#else
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static inline struct kmem_cache *
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__kmem_cache_alias(const char *name, size_t size, size_t align,
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unsigned long flags, void (*ctor)(void *))
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{ return NULL; }
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#endif
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/* Legal flag mask for kmem_cache_create(), for various configurations */
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#define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | SLAB_PANIC | \
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SLAB_DESTROY_BY_RCU | SLAB_DEBUG_OBJECTS )
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#if defined(CONFIG_DEBUG_SLAB)
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#define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
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#elif defined(CONFIG_SLUB_DEBUG)
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#define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
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SLAB_TRACE | SLAB_DEBUG_FREE)
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#else
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#define SLAB_DEBUG_FLAGS (0)
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#endif
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#if defined(CONFIG_SLAB)
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#define SLAB_CACHE_FLAGS (SLAB_MEM_SPREAD | SLAB_NOLEAKTRACE | \
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SLAB_RECLAIM_ACCOUNT | SLAB_TEMPORARY | SLAB_NOTRACK)
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#elif defined(CONFIG_SLUB)
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#define SLAB_CACHE_FLAGS (SLAB_NOLEAKTRACE | SLAB_RECLAIM_ACCOUNT | \
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SLAB_TEMPORARY | SLAB_NOTRACK)
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#else
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#define SLAB_CACHE_FLAGS (0)
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#endif
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#define CACHE_CREATE_MASK (SLAB_CORE_FLAGS | SLAB_DEBUG_FLAGS | SLAB_CACHE_FLAGS)
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int __kmem_cache_shutdown(struct kmem_cache *);
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struct seq_file;
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struct file;
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struct slabinfo {
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unsigned long active_objs;
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unsigned long num_objs;
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unsigned long active_slabs;
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unsigned long num_slabs;
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unsigned long shared_avail;
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unsigned int limit;
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unsigned int batchcount;
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unsigned int shared;
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unsigned int objects_per_slab;
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unsigned int cache_order;
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};
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void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo);
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void slabinfo_show_stats(struct seq_file *m, struct kmem_cache *s);
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ssize_t slabinfo_write(struct file *file, const char __user *buffer,
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size_t count, loff_t *ppos);
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#ifdef CONFIG_MEMCG_KMEM
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static inline bool is_root_cache(struct kmem_cache *s)
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{
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return !s->memcg_params || s->memcg_params->is_root_cache;
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}
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static inline void memcg_bind_pages(struct kmem_cache *s, int order)
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{
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if (!is_root_cache(s))
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atomic_add(1 << order, &s->memcg_params->nr_pages);
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}
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static inline void memcg_release_pages(struct kmem_cache *s, int order)
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{
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if (is_root_cache(s))
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return;
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if (atomic_sub_and_test((1 << order), &s->memcg_params->nr_pages))
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mem_cgroup_destroy_cache(s);
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}
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static inline bool slab_equal_or_root(struct kmem_cache *s,
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struct kmem_cache *p)
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{
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return (p == s) ||
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(s->memcg_params && (p == s->memcg_params->root_cache));
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}
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/*
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* We use suffixes to the name in memcg because we can't have caches
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* created in the system with the same name. But when we print them
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* locally, better refer to them with the base name
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*/
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static inline const char *cache_name(struct kmem_cache *s)
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{
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if (!is_root_cache(s))
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return s->memcg_params->root_cache->name;
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return s->name;
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}
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/*
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* Note, we protect with RCU only the memcg_caches array, not per-memcg caches.
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* That said the caller must assure the memcg's cache won't go away. Since once
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* created a memcg's cache is destroyed only along with the root cache, it is
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* true if we are going to allocate from the cache or hold a reference to the
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* root cache by other means. Otherwise, we should hold either the slab_mutex
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* or the memcg's slab_caches_mutex while calling this function and accessing
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* the returned value.
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*/
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static inline struct kmem_cache *
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cache_from_memcg_idx(struct kmem_cache *s, int idx)
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{
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struct kmem_cache *cachep;
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struct memcg_cache_params *params;
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if (!s->memcg_params)
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return NULL;
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rcu_read_lock();
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params = rcu_dereference(s->memcg_params);
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cachep = params->memcg_caches[idx];
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rcu_read_unlock();
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/*
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* Make sure we will access the up-to-date value. The code updating
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* memcg_caches issues a write barrier to match this (see
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* memcg_register_cache()).
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*/
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smp_read_barrier_depends();
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return cachep;
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}
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static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
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{
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if (is_root_cache(s))
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return s;
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return s->memcg_params->root_cache;
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}
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#else
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static inline bool is_root_cache(struct kmem_cache *s)
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{
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return true;
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}
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static inline void memcg_bind_pages(struct kmem_cache *s, int order)
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{
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}
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static inline void memcg_release_pages(struct kmem_cache *s, int order)
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{
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}
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static inline bool slab_equal_or_root(struct kmem_cache *s,
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struct kmem_cache *p)
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{
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return true;
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}
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static inline const char *cache_name(struct kmem_cache *s)
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{
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return s->name;
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}
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static inline struct kmem_cache *
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cache_from_memcg_idx(struct kmem_cache *s, int idx)
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{
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return NULL;
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}
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static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
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{
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return s;
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}
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#endif
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static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
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{
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struct kmem_cache *cachep;
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struct page *page;
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/*
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* When kmemcg is not being used, both assignments should return the
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* same value. but we don't want to pay the assignment price in that
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* case. If it is not compiled in, the compiler should be smart enough
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* to not do even the assignment. In that case, slab_equal_or_root
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* will also be a constant.
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*/
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if (!memcg_kmem_enabled() && !unlikely(s->flags & SLAB_DEBUG_FREE))
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return s;
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page = virt_to_head_page(x);
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cachep = page->slab_cache;
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if (slab_equal_or_root(cachep, s))
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return cachep;
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pr_err("%s: Wrong slab cache. %s but object is from %s\n",
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__FUNCTION__, cachep->name, s->name);
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WARN_ON_ONCE(1);
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return s;
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}
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#endif
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/*
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* The slab lists for all objects.
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*/
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struct kmem_cache_node {
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spinlock_t list_lock;
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#ifdef CONFIG_SLAB
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struct list_head slabs_partial; /* partial list first, better asm code */
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struct list_head slabs_full;
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struct list_head slabs_free;
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unsigned long free_objects;
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unsigned int free_limit;
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unsigned int colour_next; /* Per-node cache coloring */
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struct array_cache *shared; /* shared per node */
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struct array_cache **alien; /* on other nodes */
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unsigned long next_reap; /* updated without locking */
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int free_touched; /* updated without locking */
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#endif
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#ifdef CONFIG_SLUB
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unsigned long nr_partial;
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struct list_head partial;
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#ifdef CONFIG_SLUB_DEBUG
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atomic_long_t nr_slabs;
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atomic_long_t total_objects;
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struct list_head full;
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#endif
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#endif
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};
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void *slab_next(struct seq_file *m, void *p, loff_t *pos);
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void slab_stop(struct seq_file *m, void *p);
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