netdev - Re: [PATCH bpf-next] samples: bpf: refactor xdp_sample_pkts

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Message-ID: <CAEf4BzZ+tGgeqpPiKmChRYQ7FH==3AHXUK5V+Sy2tjZiO58u+w@mail.gmail.com>
Date:   Tue, 8 Sep 2020 16:24:25 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     "Daniel T. Lee" <danieltimlee@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next] samples: bpf: refactor xdp_sample_pkts_kern with
 BTF-defined map

On Sat, Sep 5, 2020 at 8:41 AM Daniel T. Lee <danieltimlee@...il.com> wrote:
>
> Most of the samples were converted to use the new BTF-defined MAP as
> they moved to libbbpf, but some of the samples were missing.
>
> Instead of using the previous BPF MAP definition, this commit refactors
> xdp_sample_pkts_kern MAP definition with the new BTF-defined MAP format.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
> ---
>  samples/bpf/xdp_sample_pkts_kern.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/samples/bpf/xdp_sample_pkts_kern.c b/samples/bpf/xdp_sample_pkts_kern.c
> index 33377289e2a8..b15172b7d455 100644
> --- a/samples/bpf/xdp_sample_pkts_kern.c
> +++ b/samples/bpf/xdp_sample_pkts_kern.c
> @@ -7,12 +7,12 @@
>  #define SAMPLE_SIZE 64ul
>  #define MAX_CPUS 128
>
> -struct bpf_map_def SEC("maps") my_map = {
> -       .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
> -       .key_size = sizeof(int),
> -       .value_size = sizeof(u32),
> -       .max_entries = MAX_CPUS,
> -};
> +struct {
> +       __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> +       __uint(key_size, sizeof(int));
> +       __uint(value_size, sizeof(u32));
> +       __uint(max_entries, MAX_CPUS);

if you drop max_entries property, libbpf will set it to the maximum
configured number of CPUs on the host, which is what you probably
want. Do you might sending v2 without MAX_CPUS (check if macro is
still used anywhere else). Thanks!

> +} my_map SEC(".maps");
>
>  SEC("xdp_sample")
>  int xdp_sample_prog(struct xdp_md *ctx)
> --
> 2.25.1
>