为什么kem_cache->节点可以分配address或array_cache？

Question

下面是mm/slab.c中的一个函数，它出现在kmem_cache的引导初始化中。我不理解这个函数，也不知道array_cache实际使用的是kmem>数组。

static void setup_node_pointer(struct kmem_cache *cachep)
{
        cachep->node = (struct kmem_cache_node **)&cachep->array[nr_cpu_ids];
}       

有人能帮我这个忙吗？

Answer 1

你有没有读过那个函数上面的注释？

/*
 * The memory after the last cpu cache pointer is used for the
 * the node pointer.
 */

板片分配器使用array变量中额外的指针空间来存储节点指针(而不是array_cache指针)。slab_def.h中的array变量上面的注释暗示了这一点

/* 6) per-cpu/per-node data, touched during every alloc/free */
/*
 * We put array[] at the end of kmem_cache, because we want to size
 * this array to nr_cpu_ids slots instead of NR_CPUS
 * (see kmem_cache_init())
 * We still use [NR_CPUS] and not [1] or [0] because cache_cache
 * is statically defined, so we reserve the max number of cpus.
 *
 * We also need to guarantee that the list is able to accomodate a
 * pointer for each node since "nodelists" uses the remainder of
 * available pointers.
 */
struct kmem_cache_node **node;
struct array_cache *array[NR_CPUS + MAX_NUMNODES];