总结完了slab创建、对象分配、对象释放，在这里再看看slab的销毁。销毁slab很简单，由函数slab_destroy()实现。
/**
* slab_destroy - destroy and release all objects in a slab
* @cachep: cache pointer being destroyed
* @slabp: slab pointer being destroyed
*
* Destroy all the objs in a slab, and release the mem back to the system.
* Before calling the slab must have been unlinked from the cache. The
* cache-lock is not held/needed.
*/
/*销毁slab，需要释放slab管理对象和slab对象。*/
static void slab_destroy(struct kmem_cache *cachep, struct slab *slabp)
{
/* 获得slab首页面的虚拟地址 */
void *addr = slabp->s_mem - slabp->colouroff;
/*调试用*/
slab_destroy_debugcheck(cachep, slabp);
if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) {
/* rcu方式释放，暂时不做分析，主要是做并行优化 */
struct slab_rcu *slab_rcu;
slab_rcu = (struct slab_rcu *)slabp;
slab_rcu->cachep = cachep;
slab_rcu->addr = addr;
call_rcu(&slab_rcu->head, kmem_rcu_free);
} else {
/* 释放slab占用的页面到伙伴系统中。如果是内置式，
slab管理对象和slab对象在一起，可以同时释放。*/
kmem_freepages(cachep, addr);
/* 外置式，还需释放slab管理对象 */
if (OFF_SLAB(cachep))
kmem_cache_free(cachep->slabp_cache, slabp);
}
}
其中，涉及到的其他函数在前面相应的地方已经做了分析。