bpf: introduce BPF_MAP_TYPE_PERCPU_HASH map
Introduce BPF_MAP_TYPE_PERCPU_HASH map type which is used to do
accurate counters without need to use BPF_XADD instruction which turned
out to be too costly for high-performance network monitoring.
In the typical use case the 'key' is the flow tuple or other long
living object that sees a lot of events per second.
bpf_map_lookup_elem() returns per-cpu area.
Example:
struct {
u32 packets;
u32 bytes;
} * ptr = bpf_map_lookup_elem(&map, &key);
/* ptr points to this_cpu area of the value, so the following
* increments will not collide with other cpus
*/
ptr->packets ++;
ptr->bytes += skb->len;
bpf_update_elem() atomically creates a new element where all per-cpu
values are zero initialized and this_cpu value is populated with
given 'value'.
Note that non-per-cpu hash map always allocates new element
and then deletes old after rcu grace period to maintain atomicity
of update. Per-cpu hash map updates element values in-place.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov
David S. Miller
parent
ba905f5e2f
commit
824bd0ce6c
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@ -81,6 +81,7 @@ enum bpf_map_type {
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BPF_MAP_TYPE_ARRAY,
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BPF_MAP_TYPE_PROG_ARRAY,
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BPF_MAP_TYPE_PERF_EVENT_ARRAY,
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BPF_MAP_TYPE_PERCPU_HASH,
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};
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enum bpf_prog_type {
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@ -31,21 +31,27 @@ struct bpf_htab {
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struct htab_elem {
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struct hlist_node hash_node;
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struct rcu_head rcu;
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u32 hash;
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union {
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u32 hash;
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u32 key_size;
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};
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char key[0] __aligned(8);
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};
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/* Called from syscall */
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static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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{
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bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_HASH;
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struct bpf_htab *htab;
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int err, i;
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u64 cost;
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htab = kzalloc(sizeof(*htab), GFP_USER);
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if (!htab)
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return ERR_PTR(-ENOMEM);
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/* mandatory map attributes */
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htab->map.map_type = attr->map_type;
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htab->map.key_size = attr->key_size;
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htab->map.value_size = attr->value_size;
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htab->map.max_entries = attr->max_entries;
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@ -77,24 +83,34 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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*/
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goto free_htab;
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if (percpu && round_up(htab->map.value_size, 8) > PCPU_MIN_UNIT_SIZE)
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/* make sure the size for pcpu_alloc() is reasonable */
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goto free_htab;
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htab->elem_size = sizeof(struct htab_elem) +
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round_up(htab->map.key_size, 8) +
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htab->map.value_size;
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round_up(htab->map.key_size, 8);
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if (percpu)
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htab->elem_size += sizeof(void *);
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else
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htab->elem_size += htab->map.value_size;
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/* prevent zero size kmalloc and check for u32 overflow */
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if (htab->n_buckets == 0 ||
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htab->n_buckets > U32_MAX / sizeof(struct bucket))
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goto free_htab;
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if ((u64) htab->n_buckets * sizeof(struct bucket) +
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(u64) htab->elem_size * htab->map.max_entries >=
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U32_MAX - PAGE_SIZE)
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cost = (u64) htab->n_buckets * sizeof(struct bucket) +
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(u64) htab->elem_size * htab->map.max_entries;
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if (percpu)
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cost += (u64) round_up(htab->map.value_size, 8) *
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num_possible_cpus() * htab->map.max_entries;
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if (cost >= U32_MAX - PAGE_SIZE)
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/* make sure page count doesn't overflow */
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goto free_htab;
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htab->map.pages = round_up(htab->n_buckets * sizeof(struct bucket) +
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htab->elem_size * htab->map.max_entries,
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PAGE_SIZE) >> PAGE_SHIFT;
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htab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
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err = -ENOMEM;
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htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct bucket),
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@ -148,7 +164,7 @@ static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
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}
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/* Called from syscall or from eBPF program */
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static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
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static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct hlist_head *head;
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@ -166,6 +182,13 @@ static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
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l = lookup_elem_raw(head, hash, key, key_size);
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return l;
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}
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static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct htab_elem *l = __htab_map_lookup_elem(map, key);
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if (l)
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return l->key + round_up(map->key_size, 8);
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@ -230,65 +253,139 @@ find_first_elem:
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return -ENOENT;
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}
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static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
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void __percpu *pptr)
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{
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*(void __percpu **)(l->key + key_size) = pptr;
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}
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static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size)
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{
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return *(void __percpu **)(l->key + key_size);
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}
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static void htab_percpu_elem_free(struct htab_elem *l)
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{
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free_percpu(htab_elem_get_ptr(l, l->key_size));
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kfree(l);
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}
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static void htab_percpu_elem_free_rcu(struct rcu_head *head)
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{
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struct htab_elem *l = container_of(head, struct htab_elem, rcu);
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htab_percpu_elem_free(l);
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}
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static void free_htab_elem(struct htab_elem *l, bool percpu, u32 key_size)
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{
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if (percpu) {
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l->key_size = key_size;
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call_rcu(&l->rcu, htab_percpu_elem_free_rcu);
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} else {
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kfree_rcu(l, rcu);
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}
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}
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static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
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void *value, u32 key_size, u32 hash,
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bool percpu)
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{
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u32 size = htab->map.value_size;
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struct htab_elem *l_new;
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void __percpu *pptr;
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l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
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if (!l_new)
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return NULL;
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memcpy(l_new->key, key, key_size);
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if (percpu) {
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/* round up value_size to 8 bytes */
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size = round_up(size, 8);
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/* alloc_percpu zero-fills */
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pptr = __alloc_percpu_gfp(size, 8, GFP_ATOMIC | __GFP_NOWARN);
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if (!pptr) {
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kfree(l_new);
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return NULL;
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}
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/* copy true value_size bytes */
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memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
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htab_elem_set_ptr(l_new, key_size, pptr);
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} else {
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memcpy(l_new->key + round_up(key_size, 8), value, size);
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}
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l_new->hash = hash;
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return l_new;
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}
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static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
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u64 map_flags)
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{
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if (!l_old && unlikely(atomic_read(&htab->count) >= htab->map.max_entries))
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/* if elem with this 'key' doesn't exist and we've reached
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* max_entries limit, fail insertion of new elem
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*/
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return -E2BIG;
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if (l_old && map_flags == BPF_NOEXIST)
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/* elem already exists */
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return -EEXIST;
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if (!l_old && map_flags == BPF_EXIST)
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/* elem doesn't exist, cannot update it */
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return -ENOENT;
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return 0;
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}
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/* Called from syscall or from eBPF program */
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static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
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u64 map_flags)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct htab_elem *l_new, *l_old;
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struct htab_elem *l_new = NULL, *l_old;
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struct hlist_head *head;
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struct bucket *b;
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unsigned long flags;
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u32 key_size;
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struct bucket *b;
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u32 key_size, hash;
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int ret;
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if (map_flags > BPF_EXIST)
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if (unlikely(map_flags > BPF_EXIST))
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/* unknown flags */
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return -EINVAL;
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WARN_ON_ONCE(!rcu_read_lock_held());
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/* allocate new element outside of lock */
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l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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/* allocate new element outside of the lock, since
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* we're most likley going to insert it
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*/
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l_new = alloc_htab_elem(htab, key, value, key_size, hash, false);
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if (!l_new)
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return -ENOMEM;
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key_size = map->key_size;
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memcpy(l_new->key, key, key_size);
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memcpy(l_new->key + round_up(key_size, 8), value, map->value_size);
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l_new->hash = htab_map_hash(l_new->key, key_size);
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b = __select_bucket(htab, l_new->hash);
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b = __select_bucket(htab, hash);
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head = &b->head;
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/* bpf_map_update_elem() can be called in_irq() */
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raw_spin_lock_irqsave(&b->lock, flags);
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l_old = lookup_elem_raw(head, l_new->hash, key, key_size);
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l_old = lookup_elem_raw(head, hash, key, key_size);
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if (!l_old && unlikely(atomic_read(&htab->count) >= map->max_entries)) {
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/* if elem with this 'key' doesn't exist and we've reached
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* max_entries limit, fail insertion of new elem
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*/
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ret = -E2BIG;
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ret = check_flags(htab, l_old, map_flags);
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if (ret)
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goto err;
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}
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if (l_old && map_flags == BPF_NOEXIST) {
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/* elem already exists */
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ret = -EEXIST;
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goto err;
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}
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if (!l_old && map_flags == BPF_EXIST) {
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/* elem doesn't exist, cannot update it */
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ret = -ENOENT;
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goto err;
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}
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/* add new element to the head of the list, so that concurrent
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* search will find it before old elem
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/* add new element to the head of the list, so that
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* concurrent search will find it before old elem
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*/
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hlist_add_head_rcu(&l_new->hash_node, head);
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if (l_old) {
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@ -298,7 +395,6 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
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atomic_inc(&htab->count);
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}
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raw_spin_unlock_irqrestore(&b->lock, flags);
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return 0;
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err:
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raw_spin_unlock_irqrestore(&b->lock, flags);
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@ -306,10 +402,64 @@ err:
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return ret;
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}
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static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
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void *value, u64 map_flags)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct htab_elem *l_new = NULL, *l_old;
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struct hlist_head *head;
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unsigned long flags;
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struct bucket *b;
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u32 key_size, hash;
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int ret;
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if (unlikely(map_flags > BPF_EXIST))
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/* unknown flags */
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return -EINVAL;
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WARN_ON_ONCE(!rcu_read_lock_held());
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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b = __select_bucket(htab, hash);
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head = &b->head;
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/* bpf_map_update_elem() can be called in_irq() */
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raw_spin_lock_irqsave(&b->lock, flags);
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l_old = lookup_elem_raw(head, hash, key, key_size);
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ret = check_flags(htab, l_old, map_flags);
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if (ret)
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goto err;
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if (l_old) {
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/* per-cpu hash map can update value in-place */
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memcpy(this_cpu_ptr(htab_elem_get_ptr(l_old, key_size)),
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value, htab->map.value_size);
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} else {
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l_new = alloc_htab_elem(htab, key, value, key_size,
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hash, true);
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if (!l_new) {
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ret = -ENOMEM;
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goto err;
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}
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hlist_add_head_rcu(&l_new->hash_node, head);
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atomic_inc(&htab->count);
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}
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ret = 0;
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err:
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raw_spin_unlock_irqrestore(&b->lock, flags);
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return ret;
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}
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/* Called from syscall or from eBPF program */
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static int htab_map_delete_elem(struct bpf_map *map, void *key)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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bool percpu = map->map_type == BPF_MAP_TYPE_PERCPU_HASH;
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struct hlist_head *head;
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struct bucket *b;
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struct htab_elem *l;
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@ -332,7 +482,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
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if (l) {
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hlist_del_rcu(&l->hash_node);
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atomic_dec(&htab->count);
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kfree_rcu(l, rcu);
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free_htab_elem(l, percpu, key_size);
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ret = 0;
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}
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@ -352,7 +502,12 @@ static void delete_all_elements(struct bpf_htab *htab)
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hlist_for_each_entry_safe(l, n, head, hash_node) {
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hlist_del_rcu(&l->hash_node);
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atomic_dec(&htab->count);
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kfree(l);
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if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH) {
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l->key_size = htab->map.key_size;
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htab_percpu_elem_free(l);
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} else {
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kfree(l);
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}
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}
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}
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}
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@ -391,9 +546,35 @@ static struct bpf_map_type_list htab_type __read_mostly = {
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.type = BPF_MAP_TYPE_HASH,
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};
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/* Called from eBPF program */
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static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct htab_elem *l = __htab_map_lookup_elem(map, key);
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if (l)
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return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
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else
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return NULL;
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}
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static const struct bpf_map_ops htab_percpu_ops = {
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.map_alloc = htab_map_alloc,
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.map_free = htab_map_free,
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.map_get_next_key = htab_map_get_next_key,
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.map_lookup_elem = htab_percpu_map_lookup_elem,
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.map_update_elem = htab_percpu_map_update_elem,
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.map_delete_elem = htab_map_delete_elem,
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};
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static struct bpf_map_type_list htab_percpu_type __read_mostly = {
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.ops = &htab_percpu_ops,
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.type = BPF_MAP_TYPE_PERCPU_HASH,
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};
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static int __init register_htab_map(void)
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{
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bpf_register_map_type(&htab_type);
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bpf_register_map_type(&htab_percpu_type);
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return 0;
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}
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late_initcall(register_htab_map);
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