> On Jun 25, 2019, at 11:12 PM, Andrii Nakryiko <andr...@fb.com> wrote:
>
> For BPF_MAP_TYPE_PERF_EVENT_ARRAY typically correct size is number of
> possible CPUs. This is impossible to specify at compilation time. This
> change adds automatic setting of PERF_EVENT_ARRAY size to number of
> system CPUs, unless non-zero size is specified explicitly. This allows
> to adjust size for advanced specific cases, while providing convenient
> and logical defaults.
>
> Signed-off-by: Andrii Nakryiko <andr...@fb.com>
> ---
> tools/lib/bpf/libbpf.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index c74cc535902a..8f2b8a081ba7 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2114,6 +2114,7 @@ static int
> bpf_object__create_maps(struct bpf_object *obj)
> {
> struct bpf_create_map_attr create_attr = {};
> + int nr_cpus = 0;
> unsigned int i;
> int err;
>
> @@ -2136,7 +2137,21 @@ bpf_object__create_maps(struct bpf_object *obj)
> create_attr.map_flags = def->map_flags;
> create_attr.key_size = def->key_size;
> create_attr.value_size = def->value_size;
> - create_attr.max_entries = def->max_entries;
> + if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY &&
> + !def->max_entries) {
> + if (!nr_cpus)
> + nr_cpus = libbpf_num_possible_cpus();
> + if (nr_cpus < 0) {
> + pr_warning("failed to determine number of
> system CPUs: %d\n",
> + nr_cpus);
> + return nr_cpus;
I think we need to goto err_out here.
Thanks,
Song
