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authorAlexei Starovoitov <ast@fb.com>2016-02-01 22:39:53 -0800
committerDavid S. Miller <davem@davemloft.net>2016-02-06 03:34:35 -0500
commit824bd0ce6c7c43a9e1e210abf124958e54d88342 (patch)
tree10d1841e462152a97c3d855f17568684d5246dd0 /kernel/bpf
parentba905f5e2f63d86ed4cfbd3d9096fb28d156f1ee (diff)
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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>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/hashtab.c275
1 files changed, 228 insertions, 47 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index c5b30fd8a315..2be5f6e8bb04 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -31,21 +31,27 @@ struct bpf_htab {
struct htab_elem {
struct hlist_node hash_node;
struct rcu_head rcu;
- u32 hash;
+ union {
+ u32 hash;
+ u32 key_size;
+ };
char key[0] __aligned(8);
};
/* Called from syscall */
static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
{
+ bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_HASH;
struct bpf_htab *htab;
int err, i;
+ u64 cost;
htab = kzalloc(sizeof(*htab), GFP_USER);
if (!htab)
return ERR_PTR(-ENOMEM);
/* mandatory map attributes */
+ htab->map.map_type = attr->map_type;
htab->map.key_size = attr->key_size;
htab->map.value_size = attr->value_size;
htab->map.max_entries = attr->max_entries;
@@ -77,24 +83,34 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
*/
goto free_htab;
+ if (percpu && round_up(htab->map.value_size, 8) > PCPU_MIN_UNIT_SIZE)
+ /* make sure the size for pcpu_alloc() is reasonable */
+ goto free_htab;
+
htab->elem_size = sizeof(struct htab_elem) +
- round_up(htab->map.key_size, 8) +
- htab->map.value_size;
+ round_up(htab->map.key_size, 8);
+ if (percpu)
+ htab->elem_size += sizeof(void *);
+ else
+ htab->elem_size += htab->map.value_size;
/* prevent zero size kmalloc and check for u32 overflow */
if (htab->n_buckets == 0 ||
htab->n_buckets > U32_MAX / sizeof(struct bucket))
goto free_htab;
- if ((u64) htab->n_buckets * sizeof(struct bucket) +
- (u64) htab->elem_size * htab->map.max_entries >=
- U32_MAX - PAGE_SIZE)
+ cost = (u64) htab->n_buckets * sizeof(struct bucket) +
+ (u64) htab->elem_size * htab->map.max_entries;
+
+ if (percpu)
+ cost += (u64) round_up(htab->map.value_size, 8) *
+ num_possible_cpus() * htab->map.max_entries;
+
+ if (cost >= U32_MAX - PAGE_SIZE)
/* make sure page count doesn't overflow */
goto free_htab;
- htab->map.pages = round_up(htab->n_buckets * sizeof(struct bucket) +
- htab->elem_size * htab->map.max_entries,
- PAGE_SIZE) >> PAGE_SHIFT;
+ htab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
err = -ENOMEM;
htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct bucket),
@@ -148,7 +164,7 @@ static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
}
/* Called from syscall or from eBPF program */
-static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
+static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct hlist_head *head;
@@ -166,6 +182,13 @@ static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
l = lookup_elem_raw(head, hash, key, key_size);
+ return l;
+}
+
+static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
+{
+ struct htab_elem *l = __htab_map_lookup_elem(map, key);
+
if (l)
return l->key + round_up(map->key_size, 8);
@@ -230,65 +253,139 @@ find_first_elem:
return -ENOENT;
}
+
+static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
+ void __percpu *pptr)
+{
+ *(void __percpu **)(l->key + key_size) = pptr;
+}
+
+static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size)
+{
+ return *(void __percpu **)(l->key + key_size);
+}
+
+static void htab_percpu_elem_free(struct htab_elem *l)
+{
+ free_percpu(htab_elem_get_ptr(l, l->key_size));
+ kfree(l);
+}
+
+static void htab_percpu_elem_free_rcu(struct rcu_head *head)
+{
+ struct htab_elem *l = container_of(head, struct htab_elem, rcu);
+
+ htab_percpu_elem_free(l);
+}
+
+static void free_htab_elem(struct htab_elem *l, bool percpu, u32 key_size)
+{
+ if (percpu) {
+ l->key_size = key_size;
+ call_rcu(&l->rcu, htab_percpu_elem_free_rcu);
+ } else {
+ kfree_rcu(l, rcu);
+ }
+}
+
+static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
+ void *value, u32 key_size, u32 hash,
+ bool percpu)
+{
+ u32 size = htab->map.value_size;
+ struct htab_elem *l_new;
+ void __percpu *pptr;
+
+ l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
+ if (!l_new)
+ return NULL;
+
+ memcpy(l_new->key, key, key_size);
+ if (percpu) {
+ /* round up value_size to 8 bytes */
+ size = round_up(size, 8);
+
+ /* alloc_percpu zero-fills */
+ pptr = __alloc_percpu_gfp(size, 8, GFP_ATOMIC | __GFP_NOWARN);
+ if (!pptr) {
+ kfree(l_new);
+ return NULL;
+ }
+
+ /* copy true value_size bytes */
+ memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
+ htab_elem_set_ptr(l_new, key_size, pptr);
+ } else {
+ memcpy(l_new->key + round_up(key_size, 8), value, size);
+ }
+
+ l_new->hash = hash;
+ return l_new;
+}
+
+static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
+ u64 map_flags)
+{
+ if (!l_old && unlikely(atomic_read(&htab->count) >= htab->map.max_entries))
+ /* if elem with this 'key' doesn't exist and we've reached
+ * max_entries limit, fail insertion of new elem
+ */
+ return -E2BIG;
+
+ if (l_old && map_flags == BPF_NOEXIST)
+ /* elem already exists */
+ return -EEXIST;
+
+ if (!l_old && map_flags == BPF_EXIST)
+ /* elem doesn't exist, cannot update it */
+ return -ENOENT;
+
+ return 0;
+}
+
/* Called from syscall or from eBPF program */
static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
- struct htab_elem *l_new, *l_old;
+ struct htab_elem *l_new = NULL, *l_old;
struct hlist_head *head;
- struct bucket *b;
unsigned long flags;
- u32 key_size;
+ struct bucket *b;
+ u32 key_size, hash;
int ret;
- if (map_flags > BPF_EXIST)
+ if (unlikely(map_flags > BPF_EXIST))
/* unknown flags */
return -EINVAL;
WARN_ON_ONCE(!rcu_read_lock_held());
- /* allocate new element outside of lock */
- l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
- if (!l_new)
- return -ENOMEM;
-
key_size = map->key_size;
- memcpy(l_new->key, key, key_size);
- memcpy(l_new->key + round_up(key_size, 8), value, map->value_size);
+ hash = htab_map_hash(key, key_size);
+
+ /* allocate new element outside of the lock, since
+ * we're most likley going to insert it
+ */
+ l_new = alloc_htab_elem(htab, key, value, key_size, hash, false);
+ if (!l_new)
+ return -ENOMEM;
- l_new->hash = htab_map_hash(l_new->key, key_size);
- b = __select_bucket(htab, l_new->hash);
+ b = __select_bucket(htab, hash);
head = &b->head;
/* bpf_map_update_elem() can be called in_irq() */
raw_spin_lock_irqsave(&b->lock, flags);
- l_old = lookup_elem_raw(head, l_new->hash, key, key_size);
+ l_old = lookup_elem_raw(head, hash, key, key_size);
- if (!l_old && unlikely(atomic_read(&htab->count) >= map->max_entries)) {
- /* if elem with this 'key' doesn't exist and we've reached
- * max_entries limit, fail insertion of new elem
- */
- ret = -E2BIG;
+ ret = check_flags(htab, l_old, map_flags);
+ if (ret)
goto err;
- }
- if (l_old && map_flags == BPF_NOEXIST) {
- /* elem already exists */
- ret = -EEXIST;
- goto err;
- }
-
- if (!l_old && map_flags == BPF_EXIST) {
- /* elem doesn't exist, cannot update it */
- ret = -ENOENT;
- goto err;
- }
-
- /* add new element to the head of the list, so that concurrent
- * search will find it before old elem
+ /* add new element to the head of the list, so that
+ * concurrent search will find it before old elem
*/
hlist_add_head_rcu(&l_new->hash_node, head);
if (l_old) {
@@ -298,7 +395,6 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
atomic_inc(&htab->count);
}
raw_spin_unlock_irqrestore(&b->lock, flags);
-
return 0;
err:
raw_spin_unlock_irqrestore(&b->lock, flags);
@@ -306,10 +402,64 @@ err:
return ret;
}
+static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
+ void *value, u64 map_flags)
+{
+ struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
+ struct htab_elem *l_new = NULL, *l_old;
+ struct hlist_head *head;
+ unsigned long flags;
+ struct bucket *b;
+ u32 key_size, hash;
+ int ret;
+
+ if (unlikely(map_flags > BPF_EXIST))
+ /* unknown flags */
+ return -EINVAL;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ key_size = map->key_size;
+
+ hash = htab_map_hash(key, key_size);
+
+ b = __select_bucket(htab, hash);
+ head = &b->head;
+
+ /* bpf_map_update_elem() can be called in_irq() */
+ raw_spin_lock_irqsave(&b->lock, flags);
+
+ l_old = lookup_elem_raw(head, hash, key, key_size);
+
+ ret = check_flags(htab, l_old, map_flags);
+ if (ret)
+ goto err;
+
+ if (l_old) {
+ /* per-cpu hash map can update value in-place */
+ memcpy(this_cpu_ptr(htab_elem_get_ptr(l_old, key_size)),
+ value, htab->map.value_size);
+ } else {
+ l_new = alloc_htab_elem(htab, key, value, key_size,
+ hash, true);
+ if (!l_new) {
+ ret = -ENOMEM;
+ goto err;
+ }
+ hlist_add_head_rcu(&l_new->hash_node, head);
+ atomic_inc(&htab->count);
+ }
+ ret = 0;
+err:
+ raw_spin_unlock_irqrestore(&b->lock, flags);
+ return ret;
+}
+
/* Called from syscall or from eBPF program */
static int htab_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
+ bool percpu = map->map_type == BPF_MAP_TYPE_PERCPU_HASH;
struct hlist_head *head;
struct bucket *b;
struct htab_elem *l;
@@ -332,7 +482,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
if (l) {
hlist_del_rcu(&l->hash_node);
atomic_dec(&htab->count);
- kfree_rcu(l, rcu);
+ free_htab_elem(l, percpu, key_size);
ret = 0;
}
@@ -352,7 +502,12 @@ static void delete_all_elements(struct bpf_htab *htab)
hlist_for_each_entry_safe(l, n, head, hash_node) {
hlist_del_rcu(&l->hash_node);
atomic_dec(&htab->count);
- kfree(l);
+ if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH) {
+ l->key_size = htab->map.key_size;
+ htab_percpu_elem_free(l);
+ } else {
+ kfree(l);
+ }
}
}
}
@@ -391,9 +546,35 @@ static struct bpf_map_type_list htab_type __read_mostly = {
.type = BPF_MAP_TYPE_HASH,
};
+/* Called from eBPF program */
+static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
+{
+ struct htab_elem *l = __htab_map_lookup_elem(map, key);
+
+ if (l)
+ return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
+ else
+ return NULL;
+}
+
+static const struct bpf_map_ops htab_percpu_ops = {
+ .map_alloc = htab_map_alloc,
+ .map_free = htab_map_free,
+ .map_get_next_key = htab_map_get_next_key,
+ .map_lookup_elem = htab_percpu_map_lookup_elem,
+ .map_update_elem = htab_percpu_map_update_elem,
+ .map_delete_elem = htab_map_delete_elem,
+};
+
+static struct bpf_map_type_list htab_percpu_type __read_mostly = {
+ .ops = &htab_percpu_ops,
+ .type = BPF_MAP_TYPE_PERCPU_HASH,
+};
+
static int __init register_htab_map(void)
{
bpf_register_map_type(&htab_type);
+ bpf_register_map_type(&htab_percpu_type);
return 0;
}
late_initcall(register_htab_map);