Commit 5e711259 authored by David S. Miller's avatar David S. Miller

Merge branch 'bpf_hash-locking'

Ming Lei says:

====================
bpf: hash: use per-bucket spinlock

This patchset tries to optimize ebpf hash map, and follows
the idea:

        Both htab_map_update_elem() and htab_map_delete_elem()
        can be called from eBPF program, and they may be in kernel
        hot path, it isn't efficient to use a per-hashtable lock
        in this two helpers, so this patch converts the lock into
        per-bucket spinlock.

With this patchset, looks the performance penalty from eBPF
decreased a lot, see the following test:

        1) run 'tools/biolatency' of bcc before running block test;

        2) run fio to test block throught over /dev/nullb0,
        (randread, 16jobs, libaio, 4k bs) and the test box
        is one 24cores(dual sockets) VM server:
        - without patchset:  607K IOPS
        - with this patchset: 1184K IOPS
        - without running eBPF prog: 1492K IOPS

TODO:
        - remove the per-hashtable atomic counter

V2:
        - fix checking on buckets size
V1:
        - fix the wrong 3/3 patch
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 26a4d063 688ecfe6
......@@ -14,11 +14,15 @@
#include <linux/filter.h>
#include <linux/vmalloc.h>
struct bucket {
struct hlist_head head;
raw_spinlock_t lock;
};
struct bpf_htab {
struct bpf_map map;
struct hlist_head *buckets;
raw_spinlock_t lock;
u32 count; /* number of elements in this hashtable */
struct bucket *buckets;
atomic_t count; /* number of elements in this hashtable */
u32 n_buckets; /* number of hash buckets */
u32 elem_size; /* size of each element in bytes */
};
......@@ -79,34 +83,35 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
/* prevent zero size kmalloc and check for u32 overflow */
if (htab->n_buckets == 0 ||
htab->n_buckets > U32_MAX / sizeof(struct hlist_head))
htab->n_buckets > U32_MAX / sizeof(struct bucket))
goto free_htab;
if ((u64) htab->n_buckets * sizeof(struct hlist_head) +
if ((u64) htab->n_buckets * sizeof(struct bucket) +
(u64) htab->elem_size * htab->map.max_entries >=
U32_MAX - PAGE_SIZE)
/* make sure page count doesn't overflow */
goto free_htab;
htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
htab->map.pages = round_up(htab->n_buckets * sizeof(struct bucket) +
htab->elem_size * htab->map.max_entries,
PAGE_SIZE) >> PAGE_SHIFT;
err = -ENOMEM;
htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head),
htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct bucket),
GFP_USER | __GFP_NOWARN);
if (!htab->buckets) {
htab->buckets = vmalloc(htab->n_buckets * sizeof(struct hlist_head));
htab->buckets = vmalloc(htab->n_buckets * sizeof(struct bucket));
if (!htab->buckets)
goto free_htab;
}
for (i = 0; i < htab->n_buckets; i++)
INIT_HLIST_HEAD(&htab->buckets[i]);
for (i = 0; i < htab->n_buckets; i++) {
INIT_HLIST_HEAD(&htab->buckets[i].head);
raw_spin_lock_init(&htab->buckets[i].lock);
}
raw_spin_lock_init(&htab->lock);
htab->count = 0;
atomic_set(&htab->count, 0);
return &htab->map;
......@@ -120,11 +125,16 @@ static inline u32 htab_map_hash(const void *key, u32 key_len)
return jhash(key, key_len, 0);
}
static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash)
static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
{
return &htab->buckets[hash & (htab->n_buckets - 1)];
}
static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash)
{
return &__select_bucket(htab, hash)->head;
}
static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
void *key, u32 key_size)
{
......@@ -227,6 +237,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct htab_elem *l_new, *l_old;
struct hlist_head *head;
struct bucket *b;
unsigned long flags;
u32 key_size;
int ret;
......@@ -248,15 +259,15 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
memcpy(l_new->key + round_up(key_size, 8), value, map->value_size);
l_new->hash = htab_map_hash(l_new->key, key_size);
b = __select_bucket(htab, l_new->hash);
head = &b->head;
/* bpf_map_update_elem() can be called in_irq() */
raw_spin_lock_irqsave(&htab->lock, flags);
head = select_bucket(htab, l_new->hash);
raw_spin_lock_irqsave(&b->lock, flags);
l_old = lookup_elem_raw(head, l_new->hash, key, key_size);
if (!l_old && unlikely(htab->count >= map->max_entries)) {
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
*/
......@@ -284,13 +295,13 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
hlist_del_rcu(&l_old->hash_node);
kfree_rcu(l_old, rcu);
} else {
htab->count++;
atomic_inc(&htab->count);
}
raw_spin_unlock_irqrestore(&htab->lock, flags);
raw_spin_unlock_irqrestore(&b->lock, flags);
return 0;
err:
raw_spin_unlock_irqrestore(&htab->lock, flags);
raw_spin_unlock_irqrestore(&b->lock, flags);
kfree(l_new);
return ret;
}
......@@ -300,6 +311,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct hlist_head *head;
struct bucket *b;
struct htab_elem *l;
unsigned long flags;
u32 hash, key_size;
......@@ -310,21 +322,21 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
key_size = map->key_size;
hash = htab_map_hash(key, key_size);
b = __select_bucket(htab, hash);
head = &b->head;
raw_spin_lock_irqsave(&htab->lock, flags);
head = select_bucket(htab, hash);
raw_spin_lock_irqsave(&b->lock, flags);
l = lookup_elem_raw(head, hash, key, key_size);
if (l) {
hlist_del_rcu(&l->hash_node);
htab->count--;
atomic_dec(&htab->count);
kfree_rcu(l, rcu);
ret = 0;
}
raw_spin_unlock_irqrestore(&htab->lock, flags);
raw_spin_unlock_irqrestore(&b->lock, flags);
return ret;
}
......@@ -339,7 +351,7 @@ 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);
htab->count--;
atomic_dec(&htab->count);
kfree(l);
}
}
......
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