slub之数据结构

struct kmem_cache_cpu {

       void **freelist;       /* Pointer to first free per cpu object */

       struct page *page;   /* The slab from which we are allocating */

       int node;         /* The node of the page (or -1 for debug) */

       unsigned int offset; /* Freepointer offset (in word units) */

       unsigned int objsize;      /* Size of an object (from kmem_cache) */

};

 

struct kmem_cache_node {

       spinlock_t list_lock;       /* Protect partial list and nr_partial */

       unsigned long nr_partial;

       struct list_head partial;

};

 

struct kmem_cache {

       /* Used for retriving partial slabs etc */

       unsigned long flags;

       int size;          /* The size of an object including meta data */

       int objsize;             /* The size of an object without meta data */

       int offset;              /* Free pointer offset. */

       struct kmem_cache_order_objects oo;

 

       /*

        * Avoid an extra cache line for UP, SMP and for the node local to

        * struct kmem_cache.

        */

       struct kmem_cache_node local_node;

       /* Allocation and freeing of slabs */

       struct kmem_cache_order_objects max;

       struct kmem_cache_order_objects min;

       gfp_t allocflags;     /* gfp flags to use on each alloc */

       int refcount;           /* Refcount for slab cache destroy */

       void (*ctor)(void *);

       int inuse;        /* Offset to metadata */

       int align;        /* Alignment */

       unsigned long min_partial;

       const char *name;   /* Name (only for display!) */

       struct list_head list; /* List of slab caches */

       struct kmem_cache_cpu cpu_slab;

};

static LIST_HEAD(slab_caches);

 

所有的kmem_caches都是串在slab_caches上的。

 

kmem_caches的成员cpu_slab指向了per-cpu结构kmem_cache_cpu

 

kmem_cache_cpu 成员freelist指向了当前空闲的object;

 

kmem_cache_cpu成员page指向当前的slab所在的page.

 

如果freelist为NULL，则证明当前所指向的page已经没有空闲，则：

1.       检查有没有部分空闲的page.

2.       |若没有则分配全新的page.

  部分空闲的page串在kmem_cache_node的成员partial上。page的成员freelist同样

用来指示是否有空闲的object可用。

  注意这个部分空闲并不指代这个page一定有空闲的object，所以，取出这个page之后要

检查page->freelist参数。如果page->freelist为NULL，则会把它从cpu cache中移除。然后重新找到一个page.当然partial是由kmem_cache_node的成员nr_partial来指示有空闲object的page个数add_partial用来增计数。