kernel hacker修炼之道之内存管理-SLUB(撤销SLAB块free_slab())

撤销SLAB块free_slab()

作者：李万鹏 于北京 borqs

SLUB分配器使用free_slab()来释放slab块。

static void free_slab(struct kmem_cache *s, struct page *page)
{
if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
struct rcu_head *head;
if (need_reserve_slab_rcu) {
int order = compound_order(page);
int offset = (PAGE_SIZE << order) - s->reserved;
VM_BUG_ON(s->reserved != sizeof(*head));
head = page_address(page) + offset;
} else {
/*
* RCU free overloads the RCU head over the LRU
*/
head = (void *)&page->lru;
}
call_rcu(head, rcu_free_slab);
} else
__free_slab(s, page);
}

static void __free_slab(struct kmem_cache *s, struct page *page)
{
/*获得页面的order*/
int order = compound_order(page);
/*获得页数*/
int pages = 1 << order;
if (kmem_cache_debug(s)) {
void *p;
slab_pad_check(s, page);
for_each_object(p, s, page_address(page),
page->objects)
check_object(s, page, p, SLUB_RED_INACTIVE);
}
kmemcheck_free_shadow(page, compound_order(page));
mod_zone_page_state(page_zone(page),
(s->flags & SLAB_RECLAIM_ACCOUNT) ?
NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
-pages);
/*清除slab标志*/
__ClearPageSlab(page);
reset_page_mapcount(page);
if (current->reclaim_state)
current->reclaim_state->reclaimed_slab += pages;
/*释放给buddy system*/
__free_pages(page, order);
}