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linux-next/include/linux/slab_def.h
Vladimir Davydov f7ce3190c4 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: Vladimir 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 18:54:09 -08:00

80 lines
1.9 KiB
C

#ifndef _LINUX_SLAB_DEF_H
#define _LINUX_SLAB_DEF_H
#include <linux/reciprocal_div.h>
/*
* Definitions unique to the original Linux SLAB allocator.
*/
struct kmem_cache {
struct array_cache __percpu *cpu_cache;
/* 1) Cache tunables. Protected by slab_mutex */
unsigned int batchcount;
unsigned int limit;
unsigned int shared;
unsigned int size;
struct reciprocal_value reciprocal_buffer_size;
/* 2) touched by every alloc & free from the backend */
unsigned int flags; /* constant flags */
unsigned int num; /* # of objs per slab */
/* 3) cache_grow/shrink */
/* order of pgs per slab (2^n) */
unsigned int gfporder;
/* force GFP flags, e.g. GFP_DMA */
gfp_t allocflags;
size_t colour; /* cache colouring range */
unsigned int colour_off; /* colour offset */
struct kmem_cache *freelist_cache;
unsigned int freelist_size;
/* constructor func */
void (*ctor)(void *obj);
/* 4) cache creation/removal */
const char *name;
struct list_head list;
int refcount;
int object_size;
int align;
/* 5) statistics */
#ifdef CONFIG_DEBUG_SLAB
unsigned long num_active;
unsigned long num_allocations;
unsigned long high_mark;
unsigned long grown;
unsigned long reaped;
unsigned long errors;
unsigned long max_freeable;
unsigned long node_allocs;
unsigned long node_frees;
unsigned long node_overflow;
atomic_t allochit;
atomic_t allocmiss;
atomic_t freehit;
atomic_t freemiss;
/*
* If debugging is enabled, then the allocator can add additional
* fields and/or padding to every object. size contains the total
* object size including these internal fields, the following two
* variables contain the offset to the user object and its size.
*/
int obj_offset;
#endif /* CONFIG_DEBUG_SLAB */
#ifdef CONFIG_MEMCG_KMEM
struct memcg_cache_params memcg_params;
#endif
struct kmem_cache_node *node[MAX_NUMNODES];
};
#endif /* _LINUX_SLAB_DEF_H */