Re: [Patch bpf-next] sock_map: include sk_psock memory overhead too

Yafang Shao
2023-03-27T03:48:50Z

On Mon, Mar 27, 2023 at 6:16 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> From: Cong Wang <cong.wang@bytedance.com>
>
> When a socket is added to a sockmap, sk_psock is allocated too as its
> sk_user_data, therefore it should be consider as an overhead of sockmap
> memory usage.
>
> Before this patch:
>
> 1: sockmap flags 0x0
> key 4B value 4B max_entries 2 memlock 656B
> pids echo-sockmap(549)
>
> After this patch:
>
> 9: sockmap flags 0x0
> key 4B value 4B max_entries 2 memlock 1824B
> pids echo-sockmap(568)
>
> Fixes: 73d2c61919e9 ("bpf, net: sock_map memory usage")
> Cc: Yafang Shao <laoar.shao@gmail.com>
> Cc: Jakub Sitnicki <jakub@cloudflare.com>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> ---
> net/core/sock_map.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index 7c189c2e2fbf..22197e565ece 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -799,9 +799,17 @@ static void sock_map_fini_seq_private(void *priv_data)
>
> static u64 sock_map_mem_usage(const struct bpf_map *map)
> {
> + struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
> u64 usage = sizeof(struct bpf_stab);
> + int i;
>
> usage += (u64)map->max_entries * sizeof(struct sock *);
> +
> + for (i = 0; i < stab->map.max_entries; i++) {

Although it adds a for-loop, the operation below is quite light. So it
looks good to me.

> + if (stab->sks[i])

Nit, stab->sks[i] can be modified in the delete path in parallel, so
there should be a READ_ONCE() here.

> + usage += sizeof(struct sk_psock);
> + }
> +
> return usage;
> }
>
> @@ -1412,7 +1420,7 @@ static u64 sock_hash_mem_usage(const struct bpf_map *map)
> u64 usage = sizeof(*htab);
>
> usage += htab->buckets_num * sizeof(struct bpf_shtab_bucket);
> - usage += atomic_read(&htab->count) * (u64)htab->elem_size;
> + usage += atomic_read(&htab->count) * ((u64)htab->elem_size + sizeof(struct sk_psock));
> return usage;
> }
>
> --
> 2.34.1
>

--
Regards
Yafang