From d7ff34d5fb5a2f6722786863c4afa79c51f8edf2 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sat, 6 Jul 2019 11:06:25 -0700 Subject: 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: Andrii Nakryiko Acked-by: Song Liu Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann --- tools/lib/bpf/libbpf.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) (limited to 'tools/lib') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index ae569b50e2e0..ed07789b3e62 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -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; - 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); + 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; -- cgit v1.2.3