Commit d7ff34d5 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs 



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: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent fb84b822

tools/lib/bpf/libbpf.c

+24 −7
Original line number Diff line number Diff line
@@ -2116,6 +2116,7 @@ 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;
@@ -2138,7 +2139,22 @@ 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;

		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);

				err = nr_cpus;

				goto err_out;

			}

			pr_debug("map '%s': setting size to %d\n",

				 map->name, nr_cpus);

			create_attr.max_entries = nr_cpus;

		} else {

			create_attr.max_entries = def->max_entries;

		}

		create_attr.btf_fd = 0;

		create_attr.btf_key_type_id = 0;

		create_attr.btf_value_type_id = 0;
@@ -2155,9 +2171,10 @@ bpf_object__create_maps(struct bpf_object *obj) 
		*pfd = bpf_create_map_xattr(&create_attr);

		if (*pfd < 0 && (create_attr.btf_key_type_id ||

				 create_attr.btf_value_type_id)) {

			cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));

			err = -errno;

			cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));

			pr_warning("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",

				   map->name, cp, errno);

				   map->name, cp, err);

			create_attr.btf_fd = 0;

			create_attr.btf_key_type_id = 0;

			create_attr.btf_value_type_id = 0;
@@ -2169,11 +2186,11 @@ bpf_object__create_maps(struct bpf_object *obj) 
		if (*pfd < 0) {

			size_t j;



			err = *pfd;

			err = -errno;

err_out:

			cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));

			pr_warning("failed to create map (name: '%s'): %s\n",

				   map->name, cp);

			cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));

			pr_warning("failed to create map (name: '%s'): %s(%d)\n",

				   map->name, cp, err);

			for (j = 0; j < i; j++)

				zclose(obj->maps[j].fd);

			return err;

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