netdev - Re: [Patch bpf-next] sock_map: include sk

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Date:   Mon, 27 Mar 2023 11:48:09 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Cong Wang <cong.wang@...edance.com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [Patch bpf-next] sock_map: include sk_psock memory overhead too

On Mon, Mar 27, 2023 at 6:16 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> From: Cong Wang <cong.wang@...edance.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@...il.com>
> Cc: Jakub Sitnicki <jakub@...udflare.com>
> Cc: John Fastabend <john.fastabend@...il.com>
> Signed-off-by: Cong Wang <cong.wang@...edance.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