[PATCH bpf-next v4 10/18] bpf: devmap memory usage

Yafang Shao
2023-03-05T12:46:39Z

A new helper is introduced to calculate the memory usage of devmap and
devmap_hash. The number of dynamically allocated elements are recored
for devmap_hash already, but not for devmap. To track the memory size of
dynamically allocated elements, this patch also count the numbers for
devmap.

The result as follows,
- before
40: devmap name count_map flags 0x80
key 4B value 4B max_entries 65536 memlock 524288B
41: devmap_hash name count_map flags 0x80
key 4B value 4B max_entries 65536 memlock 524288B

- after
40: devmap name count_map flags 0x80 <<<< no elements
key 4B value 4B max_entries 65536 memlock 524608B
41: devmap_hash name count_map flags 0x80 <<<< no elements
key 4B value 4B max_entries 65536 memlock 524608B

Note that the number of buckets is same with max_entries for devmap_hash
in this case.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
kernel/bpf/devmap.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 2675fef..19b036a 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -819,8 +819,10 @@ static int dev_map_delete_elem(struct bpf_map *map, void *key)
return -EINVAL;

old_dev = unrcu_pointer(xchg(&dtab->netdev_map[k], NULL));
- if (old_dev)
+ if (old_dev) {
call_rcu(&old_dev->rcu, __dev_map_entry_free);
+ atomic_dec((atomic_t *)&dtab->items);
+ }
return 0;
}

@@ -931,6 +933,8 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
old_dev = unrcu_pointer(xchg(&dtab->netdev_map[i], RCU_INITIALIZER(dev)));
if (old_dev)
call_rcu(&old_dev->rcu, __dev_map_entry_free);
+ else
+ atomic_inc((atomic_t *)&dtab->items);

return 0;
}
@@ -1016,6 +1020,20 @@ static int dev_hash_map_redirect(struct bpf_map *map, u64 ifindex, u64 flags)
__dev_map_hash_lookup_elem);
}

+static u64 dev_map_mem_usage(const struct bpf_map *map)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ u64 usage = sizeof(struct bpf_dtab);
+
+ if (map->map_type == BPF_MAP_TYPE_DEVMAP_HASH)
+ usage += (u64)dtab->n_buckets * sizeof(struct hlist_head);
+ else
+ usage += (u64)map->max_entries * sizeof(struct bpf_dtab_netdev *);
+ usage += atomic_read((atomic_t *)&dtab->items) *
+ (u64)sizeof(struct bpf_dtab_netdev);
+ return usage;
+}
+
BTF_ID_LIST_SINGLE(dev_map_btf_ids, struct, bpf_dtab)
const struct bpf_map_ops dev_map_ops = {
.map_meta_equal = bpf_map_meta_equal,
@@ -1026,6 +1044,7 @@ static int dev_hash_map_redirect(struct bpf_map *map, u64 ifindex, u64 flags)
.map_update_elem = dev_map_update_elem,
.map_delete_elem = dev_map_delete_elem,
.map_check_btf = map_check_no_btf,
+ .map_mem_usage = dev_map_mem_usage,
.map_btf_id = &dev_map_btf_ids[0],
.map_redirect = dev_map_redirect,
};
@@ -1039,6 +1058,7 @@ static int dev_hash_map_redirect(struct bpf_map *map, u64 ifindex, u64 flags)
.map_update_elem = dev_map_hash_update_elem,
.map_delete_elem = dev_map_hash_delete_elem,
.map_check_btf = map_check_no_btf,
+ .map_mem_usage = dev_map_mem_usage,
.map_btf_id = &dev_map_btf_ids[0],
.map_redirect = dev_hash_map_redirect,
};
@@ -1109,9 +1129,11 @@ static int dev_map_notification(struct notifier_block *notifier,
if (!dev || netdev != dev->dev)
continue;
odev = unrcu_pointer(cmpxchg(&dtab->netdev_map[i], RCU_INITIALIZER(dev), NULL));
- if (dev == odev)
+ if (dev == odev) {
call_rcu(&dev->rcu,
__dev_map_entry_free);
+ atomic_dec((atomic_t *)&dtab->items);
+ }
}
}
rcu_read_unlock();
--
1.8.3.1