学习 Linux 内存分配

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/* gfp.h */
#define alloc_pages(gfp_mask, order) \
        alloc_pages_node(numa_node_id(), gfp_mask, order)

/*
 * Allocate pages, preferring the node given as nid. When nid == NUMA_NO_NODE,
 * prefer the current CPU's closest node. Otherwise node must be valid and
 * online.
 */
static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order) {
    if (nid == NUMA_NO_NODE)
        nid = numa_mem_id();

    return __alloc_pages_node(nid, gfp_mask, order);
}

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/* Slab cache used to allocate "struct epitem" */
static struct kmem_cache *epi_cache __read_mostly;

static int __init eventpoll_init(void) {
    ...
    /* Allocates slab cache used to allocate "struct epitem" items */
    epi_cache = kmem_cache_create(
        "eventpoll_epi", sizeof(struct epitem), 0,
        SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);
    ...
}

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/*
 * Must be called with "mtx" held.
 */
static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
             struct file *tfile, int fd, int full_check) {
    ...
    struct epitem *epi;
    ...
    if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
    return -ENOMEM;
    ...
error_create_wakeup_source:
    kmem_cache_free(epi_cache, epi);

    return error;
}

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/*
 * Removes a "struct epitem" from the eventpoll RB tree and deallocates
 * all the associated resources. Must be called with "mtx" held.
 */
static int ep_remove(struct eventpoll *ep, struct epitem *epi) {
    ...
    call_rcu(&epi->rcu, epi_rcu_free);
    ...
}

static void epi_rcu_free(struct rcu_head *head) {
    struct epitem *epi = container_of(head, struct epitem, rcu);
    kmem_cache_free(epi_cache, epi);
}